Patent ID: 6236385
Filing Date: 2001-05-22
Classification: G09G

Abstract:
A method of driving a liquid crystal display device that uses a chiral nematic liquid crystal medium wherein liquid crystal molecules interposed between two substrates have a predetermined angle of twist in an initial state and said chiral nematic liquid crystal medium has two metastable states differing from said initial state as relaxation states achieved after a voltage that brings about a Freedericksz transition has been applied in said initial state, said liquid crystal display device comprising a plurality of row electrodes formed on a first one of said two substrates, each of said row electrodes being supplied with a row electrode signal, and a plurality of column electrodes formed on a second one of said two substrates, each of said column electrodes being supplied with a column electrode signal, wherein intersections between said row electrodes and said column electrodes form pixels and the voltage of a difference signal between said row electrode signal and said column electrode signal is applied to said liquid crystal corresponding to each of said pixels, said method comprising the steps of:a) during a reset period, applying to said liquid crystal a reset voltage greater than or equal to a threshold value that brings about said Freedericksz transition;b) during a first selection period after said reset period, applying to said liquid crystal a selection voltage that is selected on the basis of a critical value that brings about one of said two metastable states;c) during a non-selection period following said selection period, applying to said liquid crystal a non-selection voltage that is less than or equal to a threshold value that maintains said two metastable states;d) during a delay period between said reset period and said selection period, applying to said liquid crystal a delay voltage that is less than or equal to said critical value that brings about one of said two metastable states;e) in said column electrode signal, setting four types of potential for applying positive and negative ON selection voltages and positive and negative OFF selection voltages to said liquid crystal as said data potential;f) in said row electrode signal, setting two types of potential for applying a positive or negative reset voltage to said liquid crystal during said reset period as said reset potential, two types of potential for applying a positive or negative selection voltage to said liquid crystal during said selection period as said selection potential, and two types of potential for imposing a bias potential on said four data potentials during said non-selection period and said delay period; andg) setting either two types of said selection potential or two potentials among said four types of said data potential to be the same as said two types of said reset potential;wherein said difference signal includes within one frame said first selection period that is set to be shifted for each of said row electrodes, said non-selection period following thereafter, said reset period set before said selection period, and said delay period inserted between said reset period and said first selection period;wherein said row electrode signal is at a reset potential during said reset period, a selection potential during said first selection period, and a non-selection potential during said delay period and said non-selection period;wherein said column electrode signal is set to a data potential which includes either an ON selection potential or OFF selection potential in synchronism with said first selection period; andwhereby at least eight potential levels are used for driving said liquid, crystal.