Advancements in Thermoplastic Optical Materials for Automotive Lighting Systems

Described are strategies to maximize the performance and efficiency of long path length acrylic optical elements through material selection and manufacturing optimization. Recent LED lamp designs include functional optical elements such as light pipes and dispersion optics that channel LED light through long optical path lengths (LOPL), 5-80 cm in length. Typically, these elements are manufactured from thermoplastic optical materials such as PMMA or PC through injection molding. However, conventional thermoplastic optical materials are not suitable for LOPL application due to insufficient luminous transmission and high absorption coefficients, resulting in inadequate lamp function and poor efficiency. Furthermore, the effects of molding conditions on LOPL performance are poorly understood. Recent advancements in acrylic technology produced optimized materials for LOPL signature lighting optics: Plexiglas® HT121-LPL® and V825T-LPL® resins. Compared to conventional acrylic resins, these optimized resins increase luminous transmission 95%-101% in a 60 cm light pipe and also improve spectral transmission uniformity. Additionally, optimization of injection molding parameters including screw speed, dwell time, injection speed, and barrel temperature further increase luminous transmission 3.0%-8.2%.