Liquids have become very common in the last 20 years as displays for electronic devices. This is the result of the unusual optical and electrical properties of liquid crystals. The long thin liquid crystal molecules cause light to travel at different speeds along the molecular axis and perpendicular to that axis. This leads to their ability to rotate the plane of polarized light (see below).
These long thin molecules also have a tendency to align parallel to an applied electrical field. This response and the optical properties of liquid crystals lead to their application in various electronic devices ranging from watches and calculators to computers and televisions.
Click here for more information on liquid crystals.
Howstuffworks has a nice page describing how a LCD panel is made.
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