Reflector coatings in automobile lighting--their performance requirements, substrates, materials and processing

摘要

In the family of decorative and functional coatings, the coatings for automobile lighting reflectors have traditionally been considered "lesser" coatings that mainly provide ample reflectivity. In recent years, new lighting designs emphasize a lot more on styling than that in the past. One of the major styling changes is the use of "see-through" or clear lens instead of lens with optics on it. Therefore, the reflector coatings must provide not only reflectivity, but also an esthetically appealing appearance. For example, in the internal removable reflector design, a traditional reflector is split into two pieces, a smaller reflector and a larger decorative piece that is called a bezel. Both components presented new challenges to automobile lighting manufacturers. A small reflector generally leads to higher interior temperatures in the lamp. An aesthetic appealing appearance is more difficult to achieve on a large bezel. These lamps demand that the reflector coatings possess properties such as good barrier capability at high temperature and during cyclic thermal loading, high surface energy to alleviate "fogging," and adequate hardness for handling. Consequently, new and improved reflector coatings and process technologies are being developed. In this paper, the requirements for reflector coatings in current automobile lighting applications are reviewed. Manufacturing technologies for reflector coatings such as in-chamber topcoat, flowcoat are discussed. A comparison of various manufacturing systems including coating system based on lean manufacturing concept and centralized coating system is also provided.