Research of anti-ultraviolet nano-film structure based on the FDTD method

With the increment of awareness of health, people now pay more and more attention to the safety of sunscreen products. Inorganic sunscreen agents, such as nano- TiO2, nano- SiO2, nano- ZnO, and nano- Al2O3 are very popular among consumers for their advantages, such as the nontoxic, the odorless, not easy to decompose, not easy to undergo metamorphism, and a good ability of resisting. Based on the theory of thin film optics, two kinds of nano-films are researched and designed on the basis of the structure of photonic crystal in this paper. We conduct the simulation calculation to the transmittance of the films in the ultraviolet region with the finite-difference time-domain (FDTD) method and theoretically validate that these films can keep the ultraviolet radiation off well. Besides, the superposition of two film stacks effectively expands the width of the forbidden band against ultraviolet light. This provides a theoretical basis for the inorganic sunscreen agents applied to umbrellas coating, sunscreen coating, and anti-UV fabric and so on.