Abstract
Accurate analysis of the resin filling process into the mold cavity is necessary for the high-precision fabrication of moth-eye nanostructure using the ultraviolet nanoimprint lithography (UV-NIL) technique. In this research, a computational fluid dynamics (CFD) simulation model was proposed to reveal resin filling behavior, in which the effect of boundary slip was considered. By comparison with the experimental results, a good consistency was found, indicating that the simulation model could be used to analyze the resin filling behavior. Based on the proposed model, the effects of process parameters on resin filling behavior were analyzed, including resin viscosity, inlet velocity and resin thickness. It was found that the inlet velocity showed a more significant effect on filling height than the resin viscosity and thickness. Besides, the effects of boundary conditions on resin filling behavior were investigated, and it was found the boundary slip had a significant influence on resin filling behavior, and excellent filling results were obtained with a larger slip velocity on the mold side. This research could provide guidance for a more comprehensive understanding of the resin filling behavior during UV-NIL of subwavelength moth-eye nanostructure.
Highlights
The moth-eye nanostructure has been widely used to reduce the surface reflection on optoelectronic products, such as liquid crystal display (LCD) [1,2], solar cell [3,4], image sensor [5], etc
Based on the contrast between simulation and experimental results, the proposed simulation model considering the effect of boundary slip showed high accuracy, which could be used for the analysis of resin filling behavior during the ultraviolet nanoimprint lithography (UV-NIL) of moth-eye nanostructure
The reason for this phenomenon was that the filling height was affected by the slip velocity and resin inlet velocity simultaneously, and the filling height was mainly affected by the resin inlet velocity when the slip velocity was small while it was mainly affected by the slip velocity when the slip velocity was larger than a certain threshold [32,33]
Summary
The moth-eye nanostructure has been widely used to reduce the surface reflection on optoelectronic products, such as liquid crystal display (LCD) [1,2], solar cell [3,4], image sensor [5], etc. The ultraviolet nanoimprint lithography (UV-NIL) provides an effective solution for the high-precision fabrication of moth-eye nanostructure [8,9], which mainly includes liquid resin filling into the mold cavity and UV-curing process. Various researches have been reported to analyze resin filling behavior, the moth-eye nanostructure is generally tens to hundreds of nanometers and boundary slip has a significant effect on the filling behavior at this scale [23,24]. Based on the proposed model, the effects of process parameters and boundary conditions on resin filling behavior were investigated. A simulation model was built to investigate the resin filling behavior during UV-NIL of moth-eye nanostructure using the commercial program, ANSYS-Fluent, and the following assumptions were made to simplify the simulation process. (3) The resin was assumed as an incompressible Newton fluid [20,26]. (4) It was assumed that the resin flowed into the gap between the mold and substrate from one side at a certain speed and out from the other side [25]
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