Angular Dependence of Moiré Fringes Induced by Metal Grids for Touch Screen Panels

By way of experiments and ray tracing simulations, we investigate the angular dependence of moiré fringes induced by metal grids of various shapes (e.g., rectangular, square, hexagonal, and random metal grids) for touch screen panels (TSPs). To quantify the moiré phenomenon, we have utilized the standard deviation (SD) calculated from the simulated ray distribution. The SD value is significantly decreased (i.e., the moiré phenomenon is substantially suppressed) with the rectangular and square metal grids when the crossing angle between the metal grid and a black matrix (BM) of display panels lies within the range between 20 ^° and 60 ^°. For the hexagonal metal grid, there appears a sharp dip corresponding to the minimum SD value every 30 ^° rotation angle. However, the SD value is observed to be very high near the crossing angles at which a sharp dip occurs. Though no angular dependence arises and no moiré patterns appear with the random metal grid, yet the SD value is even higher due to point defects, compared with the rectangular and square metal grids. These results are in qualitatively good agreement with the experiment results observed with the naked eye.