The driving voltage of the liquid crystal molecules cannot be fixed at a certain value, otherwise, the liquid crystal molecules will be polarized after a long time, thereby gradually losing the 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 screen 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. Whether it is positive or negative, 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 glass layers is fixed, the grayscales displayed are exactly the same. However, in these two cases, the turning directions of the liquid crystal molecules are completely opposite, and the above-mentioned characteristic damage caused when the turning directions of the liquid crystal molecules are always fixed in one direction can be avoided. There are four common polarity transformation methods, namely, frame-by-frame phase inversion, row-by-row phase inversion, column-by-column phase inversion, and point-by-point phase inversion.
For the frame-by-frame inversion method, in the same frame, all adjacent points in the whole picture have the same polarity, while the adjacent frames have different polarities; for the line-by-line inversion method, the same line has the same polarity The polarity of the adjacent rows is different; for the column-by-column inversion method, the same column has the same polarity, but the adjacent columns have different polarities; for the point-by-point inversion method, each point The upper, lower, left, and right points adjacent to oneself have different polarities.
Most of the panel polarity conversion methods used in common personal computer liquid crystal displays are point-by-point conversion methods, because the display quality of point-by-point phase inversion is much better than other conversion methods. The table lists the performance comparisons of the four polarity conversion methods: frame-by-frame phase inversion, row-by-row phase inversion, column-by-column phase inversion and point-by-point phase inversion.
The so-called Flicker phenomenon is that the screen will have a flickering feeling, but it is not a deliberate visual effect, but because the grayscale of the displayed screen will change slightly every time the screen is updated, making people feel that the screen is flickering. . This is most likely to happen with a frame-by-frame inversion of the polarity. Because the whole picture of frame-by-frame phase inversion is of the same polarity, when the picture is positive this time, it will become negative next time. If there is a little error in the common voltage, then the positive and negative polarities will be the same gray scale. The voltage will be different, and of course the grayscale will feel different. In the case of constantly switching the screen, the Flicker phenomenon will appear because the positive and negative polarity pictures alternately appear. The polarity conversion method of other panels, although there will also be the phenomenon of Flicker, but because it is not like frame-by-frame inversion, the polarity of the entire screen is changed at the same time, only one row or one column, or even a point to change the polarity. It is not obvious to the human eye.
The so-called Crosstalk phenomenon refers to the fact that between adjacent points, the data to be displayed will affect each other, so that the displayed picture will be incorrect. Although there are many reasons for the Ctosstalk phenomenon, as long as the polarities of adjacent points are different, the occurrence of this phenomenon can be reduced.