In this article, we made a preliminary study on the main influencing factors of sparkle spots, put forward the concept of "sparklingness" to characterize the strength of sparkle spots, and proposed a standard measurement method for the sparklingness. We proposed to use 532 nm green laser pointer as the testing light source, let the light pass through the film and form a sparkle spots image at the receiving CCD or a piece of white paper. A standard image processing method was used to obtain an index number standing for the scattering status of the laser, which is defined as “sparklingness”. In the experiment, we also analyzed the power dependence of sparklingness. With proper calibration, the measurement error of the sparklingness can be minimized, and it can be used as a physical quantity to describe the film quality as of the sparkle issue. This work can be a useful reference for further study of the sparkle issue in optical films.
Acrylic (PMMA) possesses excellent optical transparency, good chemical stability as well as many other merits such as the feasibilities in dyeing and manufacturing. But its poor hardness and wear resistance restrict its industrialized applications. In order to improve the hardness and wear resistance, SiO<sub>2</sub> films were coated on PMMA substrates by both dip coating method and aerosol spraying method in this work. Heating curing method was carried out after the coating of SiO<sub>2</sub> film, and consequently, the mechanical properties, optical properties and surface morphology were characterized and compared. The experimental results showed that the SiO<sub>2</sub> films prepared by aerosol spraying method has a better performance in both hardness and wear resistance, compared with the films prepared by dip coating method. In the optimized conditions, the hardness of the PMMA was improved from 3H to ~8H, and the non-abrasion rubbing times increased from less than 100 times to 5000 times with a loading of 500g weight after the coating of SiO<sub>2</sub> film, indicating the improvement of the wear resistance.