BRIGHTNESS ENHANCEMENT FILM WITH SUBSTANTIALLY NON-IMAGING EMBEDDED DIFFUSER

摘要

A microreplicated optical film (919) for use in optical displays, backlights, and the like includes a prismatic layer (950) carried by a substrate (920). In use, the optical film may be combined in a system with other components such that the optical film is positioned between an extended light source (902) and a polarizer (904). In such cases, if the substrate has an appreciable birefringence, a subtle but characteristic colored pattern known as substrate color mura (SCM) may be detected by a user of the system. To reduce or eliminate the SCM with little or no adverse effect on brightness enhancement capabilities of the optical film, the optical film may include an embedded structured surface (933) between the substrate and the prismatic layer. In order to avoid another optical artifact known as sparkle, at least 80% of the embedded structured surface is preferably occupied by features such as defocusing lenslets or random planar facets.