| TECHNOLOGY |
A new liquid-crystal display (LCD) technology may facilitate the fabrication of displays that can be mounted onto walls or integrated into clothing, researchers in the Netherlands suggest. OPEN SANDWICH Liquid-crystal display is painted onto a single substrate. PHILIPS RESEARCH PHOTO The technique, developed employs a wet coating formulation that is painted onto a single substrate. A process known as photo-enforced stratification (PES) converts the film into micrometer-sized polymer boxes filled with liquid crystals The PES-LCD technology opens the way to make portable equipment smaller, lighter, and more robust, and also provides possibilities for making displays large enough to cover walls," says Dirk J. Broer, professor of polymer chemistry at Eindhoven University of Technology and a research fellow at Philips. The formulation, which contains a blend of liquid crystals, a mixture of monomers, an ultraviolet-light-absorbing dye, and a photoinitiator, can be painted onto a variety of substrates using standard coating technology. Closed cells of liquid crystals are formed by exposing the film to UV radiation in a two-step procedure. Exposure of the layer to high-intensity UV light through a mask induces polymerization and phase separation of the mixture, resulting in the formation of polymer walls. In the second step, a stratified polymer layer that covers the film is formed by exposing the film to low-intensity UV light at a lower wavelength. The polymer walls mechanically connect the underlying substrate to the cover and stabilize the structure. LCDs currently are produced using a technology that has been around for 25 years. In these displays, the liquid crystals are sandwiched in cells between two glass plates that are coated with electrodes, polarizers, color filters, and layers that align the liquid crystals. Vacuum suction is used to fill the cells with the liquid crystals. The whole process is time-consuming and expensive. |
| UPDATE | 05.02 |
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