The new self-luminous license plate recently unveiled by diversified technology giant 3M was instantly featured on the pages of several automotive magazines. While standard aluminum license plates are unevenly lit by a small number of lights positioned around them, the entire of the new plastic plate is brightly beaming from within, making the whole unit highly visible. The ability to discard exterior lighting elements does not just allow more freedom in customizing rear-end designs though - safety is also improved. The fact that the license plate is much more highly visible helps in avoiding rear-end collisions. "We worked in very close cooperation with 3M throughout the development process for the entire assembly and produced a solution using several of our materials. For example, we custom-made a special transparent polycarbonate film from the Makrofol®/Bayfol® product range to support the reflective film from 3M, which distributes the light evenly over the surface of the license plate," explains Dirk W. Pophusen, technical manager for polycarbonate films in the Business Development department of Bayer MaterialScience AG.
The license plate housing is made of Bayblend® T 65 and incorporates the light source, which is made up of numerous light-emitting diodes (LEDs).
The polycarbonate/ABS blend was chosen because it exhibits exceptional dimensional stability, is less prone to distortion, and remains impact-resistant in cold conditions. It also offers excellent heat resistance. The translucent front of the casing, on which the actual license details are positioned, is formed from a two-millimeter-thick sheet of the polycarbonate Makrolon®. A special technology is used to give the sheet a matt finish on one side, thus ensuring that the license details are optically isolated from the light distribution system. "The sheet also has a special surface layer that enables laser welding to create a long-lasting, tight seal between the sheet and the housing," explains Dr.
Peter Schwarz, technical product manager for polycarbonate sheets in the Business Development department of Bayer MaterialScience.
The construction is completed on the outside by the actual license plate details - a laminate consisting of the special reflective and translucent film from 3M and the carrier film from Bayer MaterialScience. "Our polycarbonate film was chosen over other materials for a variety of reasons," comments Pophusen. "For example, it bonds securely with the outer film from 3M. It is highly light permeable, exhibits good mechanical strength over a broad range of temperatures, and is resistant to the kinds of chemicals usually found in vehicles. It is also important that our films can be formed with a minimal tendency to warp when using the simple, conventional cold-stamping machines found at the license plate workshops attached to vehicle registration offices in Germany."