A cholesteric liquid crystal display (ChLCD) is a type of display technology that uses liquid crystals with a spiral structure that is chiral. This means they are organized in layers with a leading axis that varies with the layers. The pitch, or the distance over which a full rotation of 360° is completed, determines the wavelength of the reflected light. This is called Bragg reflection. Cholesteric liquid crystals are bistable and have stable states, a focal conical state (dark state) and a planar state (bright state). Unlike other displays, ChLCDs do not require any current to receive information, making them energy-efficient.
ChLCDs are highly reflective, making them easy to read, even in direct sunlight. They also have a better contrast ratio and more vivid colors compared to conventional reflective LCDs because ChLCDs reflect 50 percent of certain wavelengths, eliminating the need for color filters and polarizing layers. They are also thinner and more lightweight.
Cholesteric liquid crystals are affected by electric currents, just like other liquid crystals. Depending on the temperature and nature of a substance, they can exist in different phases, such as the nematic phase or the cholesteric phase. The cholesteric phase is used in LCDs because it responds more predictably to electric current, controlling the passage of light better.
Some examples of compounds known to form cholesteric phases are hydroxypropyl cellulose and cholesteryl benzoate.
FAQ
What is a chiral liquid crystal?
A chiral liquid crystal is a type of liquid crystal with a spiral structure and is therefore chiral. They are organized in layers, with no positional arrangement within the layers, but a leading axis that varies with the layers.
What are the advantages of ChLCDs?
ChLCDs are highly reflective, making them easy to read, even in direct sunlight. They also have a better contrast ratio and more vivid colors compared to conventional reflective LCDs. They are also thinner and more lightweight, making them ideal for portable devices.
What compounds can form cholesteric phases?
Some examples of compounds known to form cholesteric phases are hydroxypropyl cellulose and cholesteryl benzoate.
Conclusion
Cholesteric liquid crystal displays (ChLCDs) are a type of display technology that is highly reflective, energy-efficient, and has a better contrast ratio and more vivid colors compared to other reflective LCDs. They use liquid crystals with a spiral structure that is chiral, making them thin, lightweight, and easy to read in direct sunlight. This technology is also used in other applications, such as sensors and tunable lasers.
