LIQUID CRYSTAL DISPLAY (LCD) Asst.Prof.Sreelekshmi.S

LIQUID CRYSTAL Substance between a solid and a liquid layers of "rod-shaped" molecules. Within a layer, the molecules have the same orientation but differs across layers by a fixed angle twisted structure Applied voltage leads to untwisting resulting in varied orientation angles

when polarized light passes, the molecules change the polarization direction to match their own angle . Thus we can effectively rotate the polarization direction of the light wave by a certain angle.

LIQUID CRYSTAL DISPLAY Presence of light source liquid crystal sandwiched between two polarizers that have perpendicular axis of transmission. Polarizers & crystal for intensity control Red green blue filters for colour

Polarizer passes only light of polarisation same as that of its axis of transmission Light out of the liquid Crystal,is rotated by 90 degrees The voltage applied controls the amount of untwist of crystal molecules,thus limits the intensity of light Relative intensities of RGB give colour to a pixel

Advantages of LCDs Physical Size Compact and Lightweight Space saving Can be mounted on a wall or panel Power Consumption and Radiation Emission Consume less energy and more durable Consumes fewer watts than a CRT. Can reduce electric bill by 40-85%.

Viewing Does not emit Radiation Not subject to Electromagnetic Interference Viewing Cause less eyestrain Does not flicker or glare

Disadvantages of LCDs Resolution Viewing Angle Displays Native Resolutions (Resolution that it displays best) Viewing Angle Smaller, needed to be viewed more directly from the front. From the side the images on an LCD screen can seem to disappear, or invert colors.

Price Installation Response Time Upfront cost it is more costly but long-term cost but will conserve energy in the long run. Installation Need a plug interface to connect to the computer Response Time slower. The delay can cause a ghosting effect on images it displays. Requires backlight Effected by Temperature and sunlight

APPLICATIONS laptop computers digital clocks and watches microwave ovens CD players  And other electronic devices..