Abstract
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.
Highlights
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
The TiO2 thin films were prepared by pulsed laser deposition (PLD) at room temperature under P(O2) of 0.5 Pa using a TiO2 target, which was sintered at 1300 ○C for 10 h under air
A simulation of multilayer black antireflection coatings comprised of an Ag–Fe–O thin film, TiO2, and SiOxNy was successfully carried out to optimize the reflectance and transmittance properties of these stacks
Summary
Multilayer antireflective (AR) coatings have been widely studied for the improvement of the visibility of glasses and displays by reducing reflection.[1–4] The ideal reflectance spectrum can be realized by stacking transparent materials, which have high and low refractive indices (n), and optimizing their thickness as well as the number and sequence of layers.[5–7] It is expected that applying these AR techniques to transparent substrates and to light-absorbing materials will result in an increase in the light–heat conversion efficiency of solar absorbers and provide design flexibility of flat panel displays.[5,8–13] it is expected that the electric circuits underneath a flat panel display will be less visible in the turn-off state, thanks to advances in multilayer AR coatings comprised of optically black materials, which have wavelength-independent optical absorption and a higher absorption capacity. Ag–Fe–O thin films with nano-sized metal particles dispersed in an insulator matrix were prepared in an effort to compromise this trade-off relationship, and the films were shown to have both a large and constant absorption in the visible range and the high electrical resistance (Rsheet > 108 Ω⋅sq.−1).[14]. The objective of this investigation was to achieve multilayer black AR coatings with superior properties suitable for use in touch panel displays. The results of this study are expected to show the potential of simulations to optimize the design of multilayer black AR coatings for use in touch panel displays and the potential of Ag–Fe–O thin films in these stacks
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