From the mutually screwed substrate plates, a helical structure results in the liquid crystal; at a 90 ° rotated screw is referred to as TN. Incident light is polarized so before entering the liquid crystal layer linear. By the twisting of the molecules followed by a rotation of the polarization direction of light, whereby the light can pass through the second polarizer and the cell permeable to light (transparent). Since the display is in sleep mode is transparent, as this mode normally-white mode is called. If one applies an electrical voltage to the electrodes so occurs under the influence of the electric field a rotation of the liquid crystal molecules align themselves parallel to the electric field. The twisting is thus being increasingly, the polarization direction of light is no longer rotated and so that it can no longer pass through the second polarizing filter.
One assigns the polarization filters in parallel to each other, then the cell with no voltage dark and is transparent only with increasing voltage. This is called the normally-black mode. The Schadt-Helfrich cell is (as well as other liquid crystal displays) is a voltage-controlled light valve. A screen can consist of any number of such cells (picture elements, pixels) are made. In the pocket calculator has a simple 7-segment display in each case represents a number that will be in a color-capable screen for each picture element (pixel) three subpixels (subpixel) used for the primary colors red, green and blue. Samsung UN46EH5000
For STN displays (English super-twisted nematic) the twist angle of the molecules is increased to 180 ° to 270 °. Thus, a steeper electro-optical characteristics and thus an improved Multiplexbarkeit than TN displays can be achieved. Due to various technical limitations, it is only possible with some effort (double cell = DSTN cell compensation with birefringent retardation films - retarder sheets) to make the presentation a neutral color (ie, only shades of gray between black and white to produce). Instead, the yellow light conditions and the dark states are dark blue (violet tone) from.