The Simulation and Fabrication of Ag/SiO₂/Ag Thin Films Color Filter

This research is based on concepts of the Fabry-Perot principle to design a non-absorption inorganic thin film color filter to increase the saturation of color filters. To make red (R), green (G), and blue (B) color filters, the SiO₂ should possess three different thicknesses sandwiched by the silver (Ag) reflective layer. Through thin film optical software simulation, the transmittance and color saturation of R, G, and B color filters were analyzed by changing different thin film materials and thickness thereof. In addition, the actual R, G, and B color filter samples were made by pulse direct current magnetron sputtering and radio frequency magnetron sputtering, respectively. The simulated results show that Ag film has a better transmittance and color saturation than aluminum film. The effect of the magnitude of refractive index, n of SiO2 on the transmittance of R, G, and B color filters is not significant, but, it will result in the red color filter sample center peak wavelength shifts at about 20 nm. The better thicknesses of Ag/SiO₂/Ag for the color saturation as well as transmittance in R, G, and B color filters are 30 nm/170 nm/30 nm, 30 nm/131 nm/30 nm, 30 nm/100 nm/30 nm, respectively. Compared with the organic photo resistance coating color filter, this inorganic thin film color filter has better color saturation and optical transmittance than the organic photo resistance coating color filter. When the color filter deviates 15 degrees from the straight angle, the center peak wavelength of R, G, and B will shift left 15∼30 nm, and its transmittance will also decrease 1∼5%. This is because that with a larger viewing angle, the longer the path for the light has to traverse through the color filter, which would result with the change in the color wavelength as well as effect to transmittance.