Window film in its various forms is based on a polyester substrate – between 2mm and 7mm or so in thickness – which confers properties of thermal absorption and physical resilience to the surface of the glass to which it is applied. Indeed many window films are actually several individual films bonded together. Adhesive – which can typically be activated by pressure, water, or a weak solution of washing up liquid in water – is applied to one side of the film and protected by a thin, clear film, or paper, liner. The other exposed side of the film is often treated with hard acrylic coating that affords protection for the polyester against scratching and abrasion.
Window Film Technology
Two popular methods of creating window film – known as “deposition” and “sputtering” respectively – both use a vacuum chamber but there are some important differences between them.
Deposition is the less expensive method and involves drawing the film across heated metal – typically aluminium, copper, or an alloy of nickel and chromium – such that the surface of the film is “metallised” by atoms migrating from the metal. Typically this produces a darker highly mirrored surface.
Sputtering on the other hand is a more sophisticated process and involves the creation of gaseous plasma – a mixture of positively and negatively charged particles – usually from chemically inert argon atoms. The gaseous ions are accelerated under high voltage and collide with a metal “target” dislodging metal atoms as they do so. The metal atoms coat the surface of the window film – varying concentrations allow for varying colours and thermal absorption properties – and are held firmly in place by mechanical, or chemical, forces. In contrast to deposition sputtering allows the metallised coating to be microscopically thin which, in turn, allows window film with very little mirroring to be manufactured
Window Film Uses
The uses of window film are many and varied. One of the most popular applications, however, is protection against extremes of temperature – hot and cold – and the glare of direct sunlight. So-called “solar” window film can be used to reduce the unwanted build-up of heat in your home, or office, during the summer months reducing the load on your air-conditioning system. The infiltration of direct sunlight into a home, or workplace, can not only cause personal discomfort but can also be responsible for fading fabrics, furniture and fittings over time and window film can be equally beneficial in this respect, particularly in conservatories.
Window film can, of course, provide a safety barrier against flying shards of glass or sharp exposed edges if a window is broken. Untreated plate glass can be a health and safety hazard to you, your family, or your employees, but glass treated with safety window film breaks in a controlled, predictable way and the broken glass remains intact in the window frame.