Patent ID: 6057820
Filing Date: 2000-05-02
Classification: G09G

Abstract:
A method of controlling the contrast of a dot-matrix liquid crystal display that displays images having optical characteristics of individual dots responsive to voltages applied to corresponding back electrodes and a front electrode, the individual dots being grouped into a plurality of rows, the method comprising:controlling the contrast of the dot-matrix liquid crystal display by controlling the voltages applied to the row of dots in the dot-matrix liquid crystal display so that the contrast of the dot-matrix liquid crystal device is improved;the controlling further comprising applying a refresh signal to said dot-matrix liquid crystal display, switching the polarity of the voltages applied to the back electrodes of a first predetermined number of rows from a first polarity to a second polarity, switching the polarity of the voltage applied to said front electrode from the first polarity to the second polarity after the polarity of the voltages applied to the back electrodes of the first predetermined number of rows has been switched, and switching the polarity of the voltage applied to the back electrodes of the remaining rows of the dot-matrix liquid crystal display from the first polarity to the second polarity after the switching of the polarity of the voltage applied to the front electrode so that substantially none of the individual rows of the dot-matrix liquid crystal display is exposed to a voltage difference resulting from the corresponding back electrode and said front electrode being in different polarity modes for significantly more than one half the refresh cycle and the contrast of the dot-matrix liquid crystal display is improved.