Antireflective black coatings comprised of Ag–Fe–O thin films with high electrical resistivity

Black antireflective (AR) coatings with electric insulative properties are required to improve the visibility of touch panel displays in the turned-on state and their appearance in the turned-off state. In this study, multilayer black AR stacks comprised of black insulative Ag–Fe–O, high-n TiO2, and low-n SiOxNy were constructed by optical simulation and prepared using RF magnetron sputtering and pulsed laser deposition. For the stacking model with five layers, the calculations show an excellent low reflectance of below 0.15% over the whole visible range with a transmittance of 0.002%. A simulation of the three-layered model indicated that the average reflectance can be reduced from over 43% for a monolayer to 3% with a reasonable average transmittance of 15% for display applications. RF magnetron sputtering, an industrial friendly method, was used to prepare the black insulative Ag–Fe–O in the AR stack for the first time. The Ag–Fe–O thin films deposited at 200–300 °C show both a large and constant absorption coefficient over the whole visible range and an acceptable high sheet resistance. The black AR stack was comprised of the black insulative Ag–Fe–O prepared at 250 °C by RF magnetron sputtering. The observed reflectance is in good agreement with the simulated model. These results indicate the high potential of the black Ag–Fe–O films for use in AR black coatings in touch panel displays for a visually attractive turn-off appearance.