Fabrication of an LCD light guide plate using closed-die hot embossing

Hot embossing is currently applied to replicate microstructures only on one side or two opposite sides of a polymer substrate. If microstructure replication on two perpendicular sides of the substrate is necessary, closed-die hot embossing can be applied. In this study, polymethyl methacrylate (PMMA) was used as the polymer substrate. A closed die with three mold inserts was used to compress a heated PMMA substrate. Effects of related process parameters on the replication accuracy were studied. Closed-die hot embossing was compared with injection molding and injection compression molding. Results show that closed-die hot embossing can provide better replication accuracy. Optical anisotropy induced by the molding-related stresses can also be reduced.