We present a model to more accurately describe the optical properties of a twisted nematic liquid crystal display (LCD). In particular, we study the optical properties of molecules near either edge of the LCD that are unable to twist and tilt under the application of an external electric field. The properties of these layers can be deduced from the intensity transmittances measured using different configurations of the external linear polarizers. The agreement between the theoretical and the experimental transmittances is excellent, thus enabling the prediction of the actual modulation for any configuration of the polarizers. © 2000 Society of Photo-Optical Instrumentation Engineers.