Twisted Nematic Plus Dye Display
Original Publication Date: 1980-Jan-01
Included in the Prior Art Database: 2005-Feb-12
The nematic + dye (ND) cell, otherwise known as a guest-host cell, is described as a parallel aligned cell with no twist. In the off or dark state, the liquid crystal (LC) molecules, and, therefore, the dye molecules, are illuminated with light polarized parallel to the molecular long axes. Application of a field causes the molecules to rotate perpendicular to the electrodes. In this orientation the dye molecules do not absorb light efficiently, and the display appears light. However, surface forces at the electrodes and the force due to the field act in competition on the LC molecules, and only at relatively high fields is perpendicular orientation of the bulk of the LC achieved. At lower fields, a proportion of the molecules lie parallel to the electrodes and still absorb light.