常压百级洁净度环境中SiO_2薄膜稳定性

Stability of sol-gel silica coatings under ISO Class 5 atmosphere condition

在常压百级洁净度环境下,采用三种不同折射率的SiO_2溶胶在熔石英基底上涂制四种不同薄膜,利用光学理论计算模拟了三种胶体涂制的膜层稳定性,通过实验考查了膜层光学指标随时间的变化规律。SiO_2薄膜能够显著提升光学元件透射率,但由于膜层表面的大量羟基及其多孔结构,SiO_2薄膜易吸附周围环境中的有机污染物及水分填充膜层孔隙,从而导致膜层折射率发生变化,影响膜层透射率、反射率等光学性能。实验结果发现,三种溶胶凝胶化学膜在常压百级环境中的有效期为80d(绝对变化率小于0.1%),且三种胶体涂制的膜层稳定性由高到低依次为折射率1.19,1.15,1.25的膜层。

Sol-gel SiO 2 anti-reflective coatings were prepared with three different sol-gels,and their optic performance under atmosphere condition was studied in detail.Three AR coatings maintained reflective indexes of 1.15,1.19,1.25 respectively.The porous silica coatings can increase transmittance observably,but are very sensitive to contaminants and humidity in surroundings due to their strong adsorptive capacity resulting from the hydroxyl on the coatings surface and their porous structure with large specific surface area.The pores of silica coating can be filled with contaminants and humidity adsorbed on the coatings,which will increase the refractive index of the coatings and also absorb or scatter the light and therefore reduce the transmittance and increase the reflectance simultaneously.The fused silica coated with AR coatings were placed in ISO Class 5 cleanroom(ISO 14644-1)for 180 days.The results show that the optic performance change of all coatings is significant after 80 days.The AR coating with a refractive index of 1.19 is more stable comparatively.