Sun protection film

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A sun protection film is usually one of polyethylene terephthalate existing (PET) film . It is applied to windows and reduces the radiation permeability of incident sun rays. The film filters UV-A and UV-B radiation and thermal radiation. Sun protection is mainly created by reflecting the rays on the metal coating of the film and partly by absorption . Other types of sun protection are sun protection glazing , external blinds and awnings .

How a sun protection film works


The vast majority of sun protection films are made from recyclable polyethylene terephthalate. Metallized films, in the case of reflective sun protection films, are vapor-deposited with aluminum or other metals in a vacuum.


Another variant is sputtering with the cathode atomization process. In this process, an electric field between the metal block, the target, and the PET film, the substrate, causes a glow discharge in a noble gas atmosphere. This creates a plasma , i.e. H. a conductive gas consisting of neutral particles, free electrons and positive ionized noble gas atoms. The positive noble gas ions are accelerated towards the target. Upon contact with the target, metal atoms are released that hit the PET film at high speed and bond very evenly with the PET there. The advantage over conventional vapor deposition lies in the large number of metals that can be used. This allows z. B. the mirror effect that occurs with aluminum can be reduced. Likewise, PET films do not need to be colored; the color impression is then created by the choice of metal used (e.g. copper). There are Teflon-coated sun protection films for the roof area, where cleaning of the films is practically no longer necessary. The dirt cannot adhere due to the Teflon coating and is washed away with the next rain.



The structure of a modern, high-quality sun protection film consists of at least 6 layers.

  • Transparent protective film
  • Adhesive layer with UV absorbers
  • Clear or tinted polyester film with UV absorbers
  • Aluminum vapor deposition (or other metals)
  • Clear polyester film
  • Scratch-resistant coating

However, there are already some foils that can do without metal at all. The reception of GPS, radio etc. is no longer impaired with the carbon film.


Depending on the film and the type of installation, the sun's heat is reflected or absorbed . It should be noted that the higher the sun protection, the darker the film.

The rejection of the total solar energy is depending on the type of film and laying, inside or outside, up to 86% radiation reduced on the glass. The sun protection films have a UV protection of approx. 99%. In addition, a mirrored sun protection film offers protection from prying eyes during the day. Even "light" sun protection films, which can hardly be seen on the panes, achieve a radiation of almost 50% reduced on the glass and UV protection of up to 99%.

Shelf life / warranty

The durability of a high-quality film is around 15 to 20 years indoors and between 6 and 13 years outdoors, depending on the type of installation, without the film suffering any serious loss of performance. In the case of external films, the film surface should be cleaned of dirt at least once a year. Wet cleaning or cleaning of the film ensures the film's durability. Dirt or impurities burn into the film without cleaning it and destroy the film material.
The guarantee for foils is between 2.5 and 10 years for external foils and 5–15 years for internal foils, depending on the requirements and manufacturer. However, it should be compared very carefully to what these guarantees and warranties relate to.


No special previous knowledge or tools are required to coat a normal house window with sun protection film. The panes to be coated are cleaned. Each protective film has an extra, clear film to protect the adhesive. This must be removed before laying. The adhesive side and the window are sprayed with a water / detergent mixture so that no air bubbles remain under the film. The water is pushed out with the help of a doctor blade. The less water that remains under the film, the better the adhesive-glass connection.
After a drying time of approx. 4 weeks, the film has reached its final adhesion. The sun protection film remains fixed on the glass all year round. The cleaning of the windows is the same as for normal glass, but a lot of liquid and no abrasive agents should be used, as otherwise the surface coating could be scratched.
In the case of a car, it is advisable to visit a specialist workshop, as most of the windows are curved and only one specialist has the appropriate knowledge, experience and tools. When you try it yourself, blisters, kinks, and folds usually appear; Dust and hair inclusions are not uncommon. In Germany, only film material with a general operating permit or E mark is permitted. An ABE number or the E mark is printed or usually lasered on these foils. When laying, it is particularly important to ensure that the ABE number is visible on every laid film part. Films without the corresponding ABE are not permitted and, from a legal point of view, lead to the cancellation of the operating license. Complaints from the TÜV or even during police checks are to be expected and can lead to disadvantages for the vehicle driver in the event of an accident.

More protective films

In addition to the sun protection films described, other special protective films for flat glass are also used in the area of ​​splinter protection, burglar resistance , anti- graffiti , privacy protection and projection.

UV protective film
Privacy film
Structure of a patented splinter protection film
Anti-shatter films

These are mostly transparent and are used to protect against glass splinters. If the glass breaks, the foils hold the pane together and the resulting splinters are bound by the foil. No injuries can be caused by flying glass fragments. Another area of ​​application is the food manufacturing or processing industry. Here, too, the glass panes are protected by splinter protection films so that no splinters can get into production if the glass breaks.

Security films

These are manufactured up to a thickness of over 400 µm (a normal sun protection film is approx. 50 µm), e.g. B. to make break-in attempts through the glass more difficult or to prevent. They are applied to the panes from the inside. There are security films that are certified as impact-resistant in accordance with applicable standards (DIN 52290, EN 356, UL 972). Another area of ​​application is the protection of the glass against attacks etc. by glass splinters flying around like bullets. The foils are clear and do not interfere with the view through the panes in any way, but variants with integrated privacy protection (e.g. white matt) or sun protection (e.g. silver reflective) are available.

Blast-resistant security films with a thickness of approx. 475 µm offer protection in the event of an explosive attack by absorbing the surface pressure generated by a pressure wave as a result of an explosion. According to the German and European standards, such foils are tested in the pressure surge pipe.

Privacy films

These foils are available in many variations (patterns, tints) to protect against prying eyes.

Projection film

These are milk-like foils that are glued onto glass from the inside or are also used as a hanging variant. These foils provide a very sharp image in front and rear projection. There is hardly any impairment from the viewing angle.

UV protection films

UV protection films are available in clear or tinted versions. Solar control films have a UV absorber in the adhesive layer or also in the polyester material. 99% of the UV radiation is absorbed. This means that no aggressive UV light can pass through the coated glass surface. These films offer a fading protection for z. B. Window displays. One speaks of a factor of 4, which means that goods can be exposed to sunlight 4 times longer before they start to show signs of fading. Complete protection against fading cannot be achieved with a film, but the fading can be delayed.

Anti-graffiti films

They are mainly used to protect shop windows and window panes in public transport as a “sacrificial layer”. Glass surfaces are a target of sprayers, scratchings (German: scratching) or also etching (German: Ätzen). The transparent foils absorb scratches, whereby the sound and feel appear very authentic to the perpetrator, tags from spray cans and marking pens stick like a normal pane of glass. If necessary, the film can be removed without leaving any residue, the window pane does not need to be replaced.

Individual evidence

  1. 3M Prestige Window Film
  2. Example of carbon foil
  3. Example projection film