Development of LGP-based planar light source with high transmittance and unidirectional light emission

Abstract

This thesis proposed planar light source with high transmittance and unidirectional light emission. The features of high transmittance and unidirectional light emission are prerequisite for the planar light source to be used in new lighting applications such as facade sheathing and private panels. However, conventional planar light sources are opaque and emit light in both directions, so they are not suitable for new lighting applications. Therefore, a planar light source with high transmittance and unidirectional light emission is required. We applied a inverse-trapezoidal microstructure for implementing the planar light source with high transmittance and unidirectional light emission because inverse-trapezoidal structures have many advantages such as low scattering of light, controllability of emitting direction, and high transmittance. However, there are two major problems with the inverse- trapezoidal structures. The first one is that there is still light emitted to the backward direction, and the second one is that it is difficult to fabricate the inverse- trapezoidal structures, so the inverse- trapezoidal structure cannot be applied to industrial fields yet. In order to solve both problems, a new structure called a ‘light-trapping layer’ is added to inverse-trapezoidal microstructures for reducing the light emitted to the backward direction and fabrication method was improved by changing mold material and mold shape. As a result, we fabricated the planar light source with high transmittance and unidirectional light emission through mass-producible fabrication method. The ratio of backward light emission can be reduced by up to 13%, which is about 55% less than when there is no light trapping layer and the proposed fabrication process has high reproducibility and minimizes pattern deformation during pattern transfer. Also, the fabricated planar light source has high transmittance of about 80% as maximum. So it is expected that the fabricated planar light source will be applied to various novel lighting applications