Film & Foil Film & foil combo practicalities
The term, foil metallisation, is used if plastic films are coated with an extremely thin metal layer, usually between ten and eighteen microns under vacuum conditions, saysTom Kerchiss, chairman of RK Print Coat Instruments
processing however is subject to controversy and scrutiny by environmental stewards. Some say that because the manufacture of even a single tonne of aluminium may involve upwards of 1500 W/h electrical energy to convert bauxite into aluminium through the process of electrolysis that the process is wasteful, costly and environmentally damaging. Manufacturers of foil counter the environmental argument by saying that when processed it is a case of a little going a long way.
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When metallising foil the coating process is undertaken in a vacuum chamber with a gas pressure of 4 x 104 bar in the coating zone. The success of the process is dependent upon good adhesion, uniformity of appearance and good tension control when winding. Subsequent converting processes such as crosscutting, varnishing, lamination and printing make for a saleable packaged product.
Alu-foil may be used as part of a laminate structure. Generally and for reasons of economy and practicality material is produced in two metre widths and then rolled out in thicknesses of as little as six microns.
Even the sheerest of foil when used in combination with filmic structures for crisp packets and flexible pouches provide an effective barrier against gases, moisture, light and other product spoilers.
Pouches can be structured in various ways in order to meet the requirements of the food and beverage items. They may be configured for example as follows: PET/print/adhesive/metallised PET/adhesive/metallised OPP/sealant or PET/print/ adhesive/metallised OPP/sealant. PET imparts stiffness and offers good printability; the metallised filmic ply functions as a barrier against oxygen and moisture. OPP may be used as an alternative to PET as barrier and moisture resistance will be maintained but other areas of performance will be slightly altered. Pouches can of course be extruded, and a wide range of papers/films/foil may be used.
he most important coating material is aluminium foil. A material that in its raw state, bauxite, is one of the most common materials on the planet,
package printers and the brand owning customers can opt to use metallic and pearlescent inks for highlighting areas of design and promotion. Very briefly, these metallic inks incorporate aluminium platelets that serve as micro mirrors, simulating the flash and reflectivity that is normally associated with a vacuum metallised film. Pearlescent inks differ in that they use crystalline platelets, which are selective in reflecting only part of the spectra resulting in a shimmering red or green flickering effect.
Colour communication devices such as RK Print Coat Instruments FlexiProof have been supplied to manufacturers of metallic inks and pearlescent suppliers. Even more so than with traditional inks a watchful eye is needed to ensure quality is maintained at all times. As with other inks both during production and when used on press, variables such as colour repro and problems associated with how the ink interacts with the substrate need to be monitored and controlled.
Hot stamping foils are another area where foil excels. Hot stamping foil holograms can be used as registered or random patterns. They can be designed and applied as an overall pattern on a pack to maximise shelf presence. Foils in one form or another provide for almost limitless design and on-pack value added possibilities. Embossed and de- embossed labels and foil stamped labels often grace the front of wine bottles, spirits and liqueurs. For specialists operating in security and anti-counterfeiting sectors process options include but are not limited too: OVDs or optical variable devices and diffractive optical variable imaging devices DOVIDs.
Designers, converters and the consumable suppliers are not restricted to hot stamping foils and holographic images for functionality and appearance purposes or to the other technologies that have been mentioned. Flexographic label and
The FlexiProof is available as the FlexiProof 100, FlexiProof UV and FlexiProof LED UV and are invaluable prepress devices for users of flexo inks and for producers of inks, substrates and others. For print and converting plants that use multi- print processes the K Printing Proofer may be an option. This bench top device proofs using gravure, gravure-offset and flexo. Moreover wet and dry laminating samples can be taken using the gravure print head in conjunction with RK’s own K-Lam laminating accessories. A customer bespoke VCM pilot/production machine has been supplied to a manufacturer of holographic materials. For reasons of customer confidentiality specific information on this machine cannot be released.
The VCM is built to the often-exacting requirements of the customer; machines, which are sturdily constructed for wider web widths incorporate the latest drive and web control technology and is constructed in such a way that the machine may be modified should circumstances change in the future.
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April 2023
www.convertermag.com
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