Liquid crystals form the basis of modern flat screens. Merck develops special liquid crystal mixtures for each LCD technology and, as the market leader, is constantly developing new technologies. Two particular properties of liquid crystals are used for LCDs: On the one hand, they flow like liquid, but they also have the physical behavior of a crystal – anisotropic that means directionally dependent. To ensure that an LC display actually works, a layer of liquid crystal mixture with a uniform orientation must be present.
TN flat screen – function and structure
The rod-shaped liquid crystals can be arranged very differently between the layers of the LC display. If they are parallel but twisted like a spiral staircase, it is called a twisted nematic (TN) cell.
A TN flat screen is constructed from multiple layers. The ultra-thin layer of liquid crystal mixture, twisted by 90°, is located between two thin panes of glass coated with transparent electrodes. Polarization filters are found on the outside of the glass plates, while on the inside there are color filters, transparent electrodes and a two-sided layer for orienting the LC molecules. The thin layer of liquid crystals, around four to eight micrometers thick, is the heart of every LC display. When voltage is applied, the twisted arrangement of the LC molecules changes and with it, the oscillation level of the light. An LCD consists of many optical switches next to each other, called pixels, which can be controlled individually. Each pixel consists of three sub-pixels for the primary colors, which can be mixed. The pattern of light and dark pixels creates the full image seen by the viewer. Because almost no electricity flows through the LCD, this type of display is extremely energy efficient.
Find out how a liquid crystal display works and visit our LCD Explorer.
The right LCD technology for every application
Merck offers customer-specific liquid crystal mixtures for every LCD technology – such as for the classic TN technology which made the breakthrough of notebooks possible in the 1990s. Further technologies include VA (vertical alignment), IPS (in-plane switching) and FFS (fringe field switching), as well as the future technology Blue Phase. Which technology is best suited depends on the requirements of the end device.