Determining the mechanical properties of optical films in liquid crystal displays (LCDs)

Liquid crystal displays (LCDs) have become increasingly popular and have gradually replaced traditional cathode ray tube (CRT) displays. Since optical films have excellent optical properties, they are the important components of LCDs. Unfortunately, the mechanical properties of such films are unstable. This study presents an experimental methodology that combines the micro tensile test and the bulge test to characterize the mechanical properties of optical diffuser films, including Young's modulus, Poisson's ratio and residual stress. The thickness of the optical diffuser films studied herein is 38 μm. The numerical model based on finite element analysis (FEA) was employed to demonstrate that the proposed methodology successfully measures the mechanical properties of optical diffuser films in LCDs. The influence of exposure to heat on the mechanical properties of optical diffuser films was also investigated. The results reveal that the heat does significantly affects the Young's modulus of the optical diffuser films and more weakly influences the Poisson's ratio and residual stress.