Engineering Physics

8.19 Liquid crystal display (LCD)

Liquid crystals are the intermediate phases between liquid and crystal. LCDs do not generate light energy, but simply alter or control the existing light to make selected areas appear bright or dark. Liquid crystals have orientational order but lack positional order. The material that used in liquid crystal display is 4-methoxy - 4′ n-butyl benzylidene aniline (MBBA) molecules. It can act as a liquid crystal between the temperatures of 21°C to 48°C. It has an elongated rod-like structure. There are three phases in liquid crystals. They are smetic, nematic and cholestic. In smetic phase the molecules are cigar shapped and are arranged in layers. The molecules can move forward and backward but not up and down. ...