The Wikipedia entry for the history of the LCD during the 1970s and 80s, states that twisted nematic (TN) field effect LCDs were available in the 1970s. Later, in 1983, super-twisted nematic (STN) structure for passive matrix addressed LCDs was invented.
From Passive and Active-matrix, it is stated that STN requires constant refreshing:
STN LCDs have to be continuously refreshed by alternating pulsed voltages of one polarity during one frame and pulses of opposite polarity during the next frame.
whereas, apparently, the TN appears not to require refreshing, see the description of Twisted Nematics. Without wishing to quote the entire description, there is no mention of refreshing, or field reversal:
A voltage of about 1 V is required to make the crystal align itself with the field, and no current passes through the crystal itself. Thus the electrical power required for that action is very low.
So, assuming that the Wikipedia entry has not omitted something, with TN LCD was the refreshing mechanism required or not?
As an aside, if it was not, why then was it required for STN?