THE CARD BODY
The materials, construction and production of the body of the card are effectively determined
by the card’s functional components, as well as by the stresses to which it is subjected during
use. Typical functional components include:
–magnetic stripe
–signature panel
–embossing
–imprinting of personal data via laser beam (text, photo, fingerprint)
–hologram
–security printing
–invisible authentication features (e.g. fluorescence)
–chip with contacts or other coupling elements

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Figure 3.12 Classification scheme for card components

Clearly, even a relatively small card, only 0.76 mm thick, must sometimes contain a large number of functional components. This places extreme demands on the quality of the materials used and the manufacturing process. The minimum requirements relating to card robustness are specified in ISO standards 7810, 7813 and 7816 Part 1. The requirements essentially relate to the following areas:
–ultraviolet radiation
–X-ray radiation
–surface profile of the card
–mechanical robustness of the card and contacts
–electromagnetic susceptibility
–electrostatic discharges
–temperature resistance
The ISO/IEC 10373 standard specifies test methods for many of these requirements, to enable users and card manufacturers to objectively test card quality. The bending and twisting tests are particularly important for smart cards, since the chip, which is as fragile and brittle as glass, is a delicate foreign object in the elastic card. Special structural features are required to protect it against the mechanical stresses produced by bending and twisting the card. Chapter 9 contains a detailed list of tests and the methods used to perform them.

Card materials
The first material employed for ID cards, which is still widely used, is polyvinyl chloride (PVC), an amorphous thermoplastic material. It is the least expensive of all the available materials, easy to process and suitable for a wide range of applications. It is used throughout the world for credit cards. Its drawbacks are a limited lifetime, due to physical deterioration, and limited resistance to heat and cold. PVC is used in sheet form to manufacture cards, since injection molding is not possible. The worldwide production of PVC was around 13 million metric tons in 1996, of which 35,000 metric tons (0.27 %) were used for cards. PVC is considered to be environmentally hazardous, since the feedstock, vinyl chloride, is a known carcinogen. In addition, if it is burned, hydrochloric acid and (under unfavorable conditions) possibly dioxins are released. In addition, heavy-metal compounds are often used as stabilizers. Nonetheless, PVC is still by far the most widely used material for cards. This is primarily due to its low
price and good processing characteristics. However, it used less and less each year due to its undesirable environmental properties. Many card issuers have decided not to use PVC for reasons of environmental policy.

To avoid the drawbacks of PVC, acrylonitrile butadiene styrene (ABS) has been used for some time to make cards. It is also an amorphous thermoplastic that is distinguished
by its stability and resistance to temperature extremes. Consequently, it is often used for cards for mobile telephones, which for obvious reasons may be subjected to relatively high temperatures. ABS can be processed both in sheet form and by injection molding. Its major drawbacks are limited ink acceptance and low weathering resistance. Although the feedstock for ABS production, benzene, is a carcinogen, ABS has no other known environmental drawbacks.

For applications in which extreme stability and durability are required, polycarbonate (PC) is used. It is typically used for identity cards, and it is incidentally the base material for compact discs and DVDs. Due to its high thermal stability, relatively high temperatures are needed to apply holograms or magnetic stripes using the hot-stamp process. This can easily cause problems, due to the limited thermal stability of the materials being applied. The main drawbacks of polycarbonate are its low degree of resistance to scratching and very high cost compared with other card materials. A further drawback is that phosgene and chlorine are needed for the production of polycarbonate, and both of these materials are environmentally problematical. Polycarbonate cards can be easily recognized by the characteristic ‘tinny’ sound they produce when dropped on a hard surface.

An environmentally friendly material that is mainly used as a PVC substitute is polyethylene terephthalate (PET), which has been used for a relatively long time to make packaging materials. It is commonly known as polyester. This thermoplastic material is used in smart cards in both its amorphous form (A-PET) and its crystalline form (PETP). Both types are suitable for processing in sheet form, as well as by injection molding. However, PETP is difficult to laminate, which makes additional processing steps necessary in the manufacturing process.

Numerous attempts have been made to find new or better materials for card bodies besides the usual materials (PVC, ABS, PC and PET). One example is cellulose acetate, which although having good environmental properties, has up to now proven to be poorly suited to the mass production of cards. Truly different materials, such as paper, have been frequently discussed, but as yet they have never been used in any significant quantity. The requirements imposed on cards, in terms of cost, durability and quality, are after all very high, and they can presently only be met by plastics. In 1996 and 1997, Danmont conducted a field trial using around 600 cards that, while they did not represent a real alternative to plastic card bodies, were at least an interesting (or amusing) idea. The cards were laminated from eight layers of birch wood, each 0.1 mm thick. These cards did not meet the requirements of the various tests specified in ISO 10 373, such as those for bending and twisting, and they were naturally not suitable for embossing. However,
around 90% of their users expressed a positive reaction and said that they experienced no problems with their cards. Unfortunately, a birchwood card is not especially innovative from an environmental perspective, since the layers must be laminated using a plastic adhesive and the usual printing processes are required.

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Figure 3.13 Structural formulae of the most important materials used for card bodies

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