The purpose of printing inks in blister packaging is provide graphics and aesthetic appeal. They can be applied to the lidding material by letterpress, gravure, off-set, flexographic, or silk-screen printing processes.

Printing inks requirements for blister packaginf:
  • resist heat- sealing temperatures as high as 300 8C without showing any discoloration or tackiness (blocking).
  • resist abrasion, bending, and fading
  • safe for use with the intended product
  • should not contain excessive amounts of hydrocarbon lubricants, greases, oils, or release agents.
Cold-formed foil/foil
Best known blister package is made from foil, film, paper, or multimaterial backing that is adhered to a sheet of thermoformed plastic blisters. However, a less common type of blister is the foil/foil lamination used for products that are particularly susceptible to moisture and/or light. Unlike all-plastic blisters, these are not thermoformed but instead are cold-pressed into shape. Products that require the highest degree of protection are packed in an all-foil package. Cold-formable foil is finding favor because it is the only material that provides a 100% barrier to moisture, oxygen, and light. This has helped expand the applications in which blisters can be used, allowing the blister packaging of sensitive products.

One element of the foil/foil blister pack comprises a lamination of plastic film (PVC or PE), adhesive, foil, adhesive, and an outer plastic film. The outer film, which can be PET or PVC, supports the thin aluminum layer and acts as the heat-seal layer. The aluminum layer usually consists of several very thin layers rather than a single thick one. The multiple layers help ensure that pinholes do not go all the way through the foil. They also increase the stretchability of the metal and facilitate the cold-stretching process. Even so, the brittleness of cold-formed aluminum means that foil/foil blisters can not be made as formfitting as plastic ones. These multilayer webs are formed, filled, and sealed on a machine that performs these functions in sequence much as the thermoform–fill–seal machine does except that neither web is heated before the forming step.

During the cold-forming process, the foil is shaped and molded around a plug to form a cavity. It is a marginally more expensive process than thermoforming, and its tooling is a bit more expensive than that of thermoformers. Most new machines can be converted to cold-form aluminum. One disadvantage is that the cavities must be made larger in the cold-forming process than during thermoforming, thus increasing the overall area of the package and often allowing the product to shift inside the blister.

Read more :