They contain too few crystals to hold a permanent configuration together. Bulk crystalline rearrangement gives embossed PET unexpected and useful optical properties, Theo Tervoort at ETH Zentrum, Switzerland, and colleagues now report in the journal Advanced Materials . The novel material splits light into two polarized beams and this means that that PET can be used in LCDs. Liquid crystals in a display act as a kind of valve controlling the flow of polarized light towards a filter. Imagine the filter as a horizontal letterbox and light as a vertical envelope.
Liquid crystals rotate the light so that it fits through the filter.
Symbols and numbers on an LCD screen are black shapes through which light cannot pass. They block horizontal envelopes, which when rotated will not fit through the horizontal letterbox. This wastes half of the light and makes LCD screens dim. The polymer film devised by Tervoot's team is a more efficient polarizing device. One of the two polarized light beams separated by the polymer is 'correctly' orientated.