| 摘要 |
A method for optimising the contrast of field-effect liquid crystal cells without having to depart from the technically proved, cost-effective technology for the production of large-area liquid crystal display devices having negative contrast representation, such as are applied, in particular, for motor vehicle instrumentation, consists in measuring for a given cell with liquid crystal filling that transmitted light wavelength at which the cell driven electrooptically to block passes through a minimum in its characteristic of the residual transmission over the light wavelength, that is to say experiences maximum absorption. The transmission operation of the liquid crystal cell is then performed by means of light in the spectral region about this wavelength, which light is filtered out from the light of an illuminating arrangement by means of a colour foil. The temperature dependence of the residual transmission is decisively reduced if a dichroitic dye is added at low concentration to the liquid crystal material, being chosen in accordance with the transmitted light colour. Pole filter pairings which optimally block for the light wavelength previously determined can be selected experimentally for the purpose of further contrast optimisation. |
