Development of Anti-Spy Privacy Films with Controlled Viewing Angle by Using UV Nanoimprint Lithography and Nanoink Filling

Abstract

Anti-spy privacy films that can block information by reducing the viewing angle of the display screen were fabricated with the UV nanoimprint lithography process and nanoink filling method. An Optis-works simulation showed that the relative luminance ratio measured at the side angle of 30 degrees relative to the front side (RLR at 30 degrees) had the lowest value at 0.66 when an isosceles trapezoidal pattern shape was adopted. Based on the simulation results, a microlouver layer with the isosceles trapezoidal pattern shape was formed on a PET film with the UV nanoimprint lithography process. Then, nanoink sols with a high refractive index were injected between the microlouver patterns to improve the security performance. When nanoinks with high viscosity or solvents with low volatility were used, stiction phenomenon occurred, and the pattern was deformed during the evaporation of the solvent in the nanoink. The CuO-filled film had an RLR at 60 degrees of 0.23, which showed the best optical protection characteristics; however, its transmittance was as low as 30% at a wavelength of 550 nm. When a ZrO2 nanoink was used to fill the film, its RLR at 60 degrees had a relatively good value of 0.80, and it exhibited a high transmittance of 59%