Novel Method For Fabrication Anti-reflection Coating With “moth-eye” Nanostructure And The Color Of The Coated Fine-denier Polyester Fabrics

Anti-reflection coatings with “Moth-eye” like structure show gradient refractive index between air and coating surface and prevent the light reflecting off the coating surface. This anti-reflection feature exhibits either wavelength independence or incident angle independence properties, providing the coating with efficient broadband antireflective performance. As a result, the coated colored substrates exhibit good color reproduction.“Sol-gel” particles have a circular shape profile being similar to nano-pillar array at “moth-eye” surface, which can be used to prepare “moth-eye” like structure anti-reflection coatings. The key to eliminating the dependence on visible-wavelength and fabricating efficient anti-reflection coating is large-size particles, while avoiding the light scattering caused by the formed large size bulges. In this study, we reported a novel method to fabricate “moth-eye” like anti-reflection coatings exhibiting visible wavelength-independent properties.Firstly, a commercially available 20 nm SiO₂ particle was diluted as coating solution. The influence of concentration of coating solution on the Z-SiNP coating thickness, surface morphology and anti-reflective properties were discussed. Results indicated that: the surface of Z-SiNP coating presented “spherical protuberance” morphology and the protuberance had the same size as that of single SiO₂ particle. The Z-SiNP coating enhanced the transmittance of substrate in the visible region, but the transmission spectrum showed wave characteristics, suggesting its obvious wavelength dependency. In addition, with the increase of coating solution concentration, the coating thickness increased. The fluctuation of transmission spectrum was even more significant, indicating the multilayer structure of Z-SiNP coating.Then, Z-SiNP was modified with tetraethoxysilane（TEOS） to prepare T-SiNP. After characterization of T-SiNP particles, T-SiNP dispersion was coated on quartz substrate.The formation mechanism of surface morphology and the anti-reflective properties were investigated. The results showed that: the ethoxy segments originated from TEOS were covalently linked to Z-SiNP, the absolute value of zeta potential decreased and the dispersion stability was slightly lower than bare Z-SiNP particles. The modification resulted in aggregation of T-SiNP during coating formation, which assembled to form large aggregates with stable porous structure. The possible reason was related to the anchored ethoxy groups that resulted into coating with “moth-eye” structures. Furthermore, the increase of the concentration of coating solution increased the coating thickness, while the “moth-eye” morphology changed little. The modification degree had little effect on the “moth-eye” morphology. The T-SiNP coating exhibited visible wavelength-independent transmittance enhancement for substrate. The coated colored substrates display deepened colors without sacrificing of any color hues, and its color reproduction was remarkably better than Z-SiNP coating.Fine-denier polyester fabric are difficult to obtain full shaded color especially in black or other dark colors, due to its intrinsic large refractive index and high specific surface area. Anti-reflective deepening is an important means to improve the apparent color depth of fine-denier polyester. To this end, Z-SiNP and T-SiNP were used as color deepening agents for finishing fine-denier polyester fabrics by padding process. Then the color deepening properties of the agent and its effects on the wearability of fine-denier polyester fabric were investigated. Results indicated that: compared to Z-SiNP, T-SiNP formed looser nanoporous coating on fabric surface, which could be more efficient to reduce the reflectance and improve the color depth of fabrics. By applying the optimized finishing process, the deepening degree reached 28.5% when mass concentration of T-SiNP that attached to fabric was as low as 1.5%. After finishing, the fabric showed good washing fastness, due to the bonding between T-SiNP and plastified polyester during baking finishing. Thus, after seven times washing cycles, the deepening degree was still up to 20%. The hues of polyester fabrics with three primary colors changed little after being finished with T-SiNP. Furthermore, T-SiNP improved the hydrophilicity of the finished polyester fabrics. One drawback of the finished fabrics was the poor friction color fastness.