The driving voltage of the liquid crystal molecules cannot be fixed at a certain value. Otherwise, over time, the liquid crystal molecules will be polarized and gradually lose their optical rotation characteristics. Therefore, in order to avoid the destruction of the characteristics of the liquid crystal molecules, the driving voltage of the liquid crystal molecules must be polarized, which requires the display voltage in the liquid crystal display to be divided into two polarities, one is positive and the other is negative. When the voltage of the display electrode is higher than the common electrode voltage, it is called positive polarity; when the voltage of the display electrode is lower than the common electrode voltage, it is called negative polarity. Regardless of whether it is positive or negative polarity, there will be a set of grayscales with the same brightness, so when the absolute value of the pressure difference between the upper and lower layers of glass is fixed, the grayscale displayed is exactly the same. However, in these two cases, the direction of the liquid crystal molecules is completely opposite, which can avoid the above-mentioned characteristic destruction caused by the direction of the liquid crystal molecules being fixed in one direction. There are four common polarity conversion methods, namely frame-by-frame inversion, line-by-line inversion, column-by-column inversion, and point-by-point inversion.
For the frame-by-frame inversion method, in the same frame, all adjacent points of the entire screen have the same polarity, while the adjacent frames have different polarities; for the row-by-row inversion method, the same polarity is on the same row, while the adjacent rows have different polarities; for the column-by-column inversion method, the same polarity is on the same column, while the adjacent columns have different polarities; for the point-by-point inversion method, the polarity of each point is different from that of the four points above, below, left, and right adjacent to it.
Most of the panel polarity conversion methods used in common personal computer LCD screens are point-by-point conversion methods, because the display quality of point-by-point inversion is much better than other conversion methods. The table lists the performance comparison of the four polarity conversion methods of frame-by-frame inversion, row-by-row inversion, column-by-column inversion, and point-by-point inversion.
The so-called Flicker phenomenon is that the picture will have a flickering feeling, but it is not a deliberately made visual effect, but because the grayscale of the displayed picture will have some slight changes every time the picture is updated, which makes the human eye feel that the picture is flickering. This is most likely to happen when using the frame-by-frame inversion polarity conversion method. Because the entire screen of the frame-by-frame inversion is of the same polarity, when the screen is positive this time, it will become negative next time. If there is a slight error in the common voltage, the voltage of the same grayscale of positive and negative polarity will be different, and of course the grayscale feeling will be different. When the screen is switched continuously, the positive and negative polarity screens appear alternately, and the flicker phenomenon will occur. Although the polarity change method of other panels will also have this flicker phenomenon, it is not like the frame-by-frame inversion, which changes the polarity of the entire screen at the same time. Only one row or one column, or even one point changes polarity. From the perspective of the human eye, it will not be obvious. The so-called Crosstalk phenomenon refers to the situation that the data to be displayed between adjacent points will affect each other, so that the displayed picture will be incorrect. Although there are many causes of the Crosstalk phenomenon, as long as the polarity of adjacent points is different, the occurrence of this phenomenon can be reduced.