Suppression of Moiré Phenomenon Induced by Metal Grids for Touch Screen Panels

With attempt to suppress the Moiré phenomenon, we conduct ray tracing simulations with various metal grids having different degree of randomness (e.g., rectangular, width-altered rectangular, line-shifted rectangular, wavy square, and random metal grids) in the presence of twisted nematic (TN) or in-plane switching (IPS) mode black matrix (BM). We analyze their angular dependence in terms of the standard deviation (SD) calculated from the simulated ray distribution. It is observed that metal grids with a lower degree of randomness exhibit a stronger angular dependence, yet lower SD value over the broader range of crossing angles. Though metal grids with a higher degree of randomness show a weaker angular dependence, yet they bring in higher fluctuation in the SD value due most likely to point defects. The wavy square metal grid results in periodic point defects, whereas the random metal grid gives rise to aperiodic point defects. Through a comparison between simulation and experiment results, we have found that moiré patterns are hardly seen to the naked eye when the SD value is less than 10, which provides useful design guidelines of metal grids.