Liquid Crystal Technology OverviewIntroductionLiquid CrystalDielectric anisotropy PropertySlide 5Twisted Nematic LCSlide 7Twisted Nematic LC DisplayPassive matrix LCDSuper Twisted Nematic DisplaysSlide 11TFT Active Matrix LCDApplicationsSlide 14Order ParameterLiquid Crystal Technology OverviewECE-E443Kai Chung WongIntroductionThe study of liquid crystals began in 1888 when an Austrian botanist named Friedrich Reinitzer observed that a material known as cholesteryl benzoate had two distinct melting points. He increased the temperature of a solid sample and watched the crystal change into a hazy liquidLiquid CrystalCharacteristic •Organic substance in the state between solid and Liquid state•Temperature between Tm and Tc•Thin and Elongated structure•Strong dipoles or easily polarizable substituentsDielectric anisotropy PropertyPositive dielectric anisotropyMolecules will align parallel with electric fieldNegative dielectric anisotropyMolecules will align perpendicular with electric fieldThe index of refraction is larger along with the long axis of the moleculesAnisotropies of LC enable the index of refraction to be controlled electricallyAnisotropy: Dielectric Constant+++++- -- --EE++++----positivenegativeall angles inthe plane to E arepossible for the- materialsETwisted Nematic LC•Twisted nematic liquid crystal acts as a polarization rotator, with polarization plane rotating in alignment with the molecular twist.Twisted Nematic LC Displayliquid crystal place between two polarizerAlignment layer force molecules orientate in the direction of the polarization planeLight follows the helix shaped moleculesPassive matrix LCDSuper Twisted Nematic DisplaysTFT Active Matrix LCDApplicationsLC DisplaySensorTemperaturePressureChemicalWDMQuestions?Order