In order to sufficiently save the power consumption and to lower the withstand voltage of elements, by having one data signal line per one row of pixels and one scanning signal line per one line of pixels, the polarity of data written in the data signal line is varied each one field period....http://www.google.com/patents/US5748165?utm_source=gb-gplus-sharePatent US5748165 - Image display device with plural data driving circuits for driving the display at different voltage magnitudes and polarity 
