A colour-separating backlight can be made by using a surface-relief grating as an outcoupling structure on top of a lightguide. By combining such a structure with a birefringent layer, a polarised colour-separating backlight can be realised. We discuss experiments and simulations on a prototype of such backlight structures, as well as directions how to optimise them. First optimised samples of gratings made by laser-interference lithography show promising results.
Polymeric relief structures are extensively used in display technology due to their ability to redirect light in a controlled way. Photo-embossing is a new photo-lithographic technique to generate surface relief structures using photopolymers. In the present paper we show a combinatorial methodology to explore this technique. We have prepared and evaluated (using automated atomic force microscopy) 2-dimensional libraries of photo-embossed gratings, each library with a gradient in period and a gradient in either exposure energy or development temperature or film thickness or photoinitiator concentration or monomer to binder ratio. We show how this combinatorial approach helps us to better understand the photo-embossing process. In addition, we show that this methodology is an effective tool to identify processing conditions resulting in optimum shape and height of the polymeric relief micro-structures to be used in specific applications.
New designs are presented of backlight systems for transmissive and transflective LCD’s based on stretched PET films with a well-defined micro-structure, which emit highly collimated or diffuse and linearly polarized light with a high efficiency. Moreover, edge-lit waveguide systems are discussed equipped slanted phase gratings which combine a range of desirable features such as a high transparency in direct view, a direct emission of light at normal angles to the plane of the waveguide and a purely unidirectional out-coupling of light towards the LCD-side. Moreover, these illumination systems emit colored, linearly polarized light which should contribute significantly to the energy efficiency of transmissive, transflective and reflective LCD displays.