Commonly used polarity conversion method for TFT liquid crystal display

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 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. This requires the display voltage in the LCD screento be divided into two polarities, one is positive polarity and the other is negative polarity. . When the voltage of the display electrode is higher than the voltage of the common electrode, it is called positive polarity; when the voltage of the display electrode is lower than the voltage of the common electrode, it is called negative polarity. Regardless of the positive polarity or the negative polarity, there will be a set of gray scales with the same brightness, so when the absolute value of the pressure difference between the upper and lower glass layers is fixed, the gray scales displayed are exactly the same. However, in these two cases, the turning of the liquid crystal molecules is completely opposite, which can avoid the above-mentioned characteristic damage caused when the turning of the liquid crystal molecules is always fixed in one direction. There are four common polarity conversion modes, namely, frame-by-frame phase inversion, line-by-line phase inversion, column-by-column phase inversion, and point-by-point phase inversion, as shown in Figure 1. Figure 1 Polarity conversion method of the LCD screen can be seen from Figure 1. For the frame-by-frame phase inversion method, in the same frame, all adjacent points of the entire screen have the same polarity, while the adjacent frame poles The gender is different; for the row-by-row phase inversion method, the same polarity is on the same row, but the polarity of adjacent rows is different; for the column-by-column phase inversion method, the polarity is the same on the same column, but adjacent The column polarity is different; for the point-by-point phase inversion mode, each point is adjacent to the four points up, down, left, and right, and the polarity is different. At present, the common LCD screens of personal computers, most of the panel polarity conversion methods used are point-by-point conversion methods. Why? The reason is that the display quality of point-by-point phase inversion is much better than other conversion methods. The table lists the performance comparison of the four polarity conversion modes: frame-by-frame phase inversion, line-by-line phase inversion, column-by-column phase inversion, and point-by-point phase inversion. Table four polarity conversion methods performance comparison The so-called Flicker phenomenon is that the screen will feel flickering, but it is not a deliberate visual effect, but because the displayed screen grayscale will slightly change every time the screen is updated. , Let people feel that the picture is flickering. This situation is most likely to occur using the polarity conversion method of frame-by-frame phase reversal. Because the whole picture of the phase inversion frame by frame is the same polarity, when the picture is positive this time, it will become negative polarity next time. If the common voltage has a little error, then the positive and negative polarity will be the same gray scale. There will be a difference in voltage, and of course the feeling of gray scale is also different, as shown in Figure 2. In the case of constantly switching screens, the Flicker phenomenon will appear due to the alternate appearance of positive and negative screens. The polarity change method of other panels may also have this Flicker phenomenon, but because unlike the frame-by-frame phase reversal, the entire screen changes the polarity at the same time. There is only one row or one column, and even one point changes the polarity. As far as the human eye is concerned, it will not be obvious. Figure 2 Causes of Ficker phenomenon The so-called Crosstalk phenomenon refers to the fact that between adjacent points, the data to be displayed will affect the other party, so that the displayed picture will be incorrect. Although there are many causes of the Ctosstalk phenomenon, as long as the polarities of adjacent points are different, the occurrence of this phenomenon can be reduced. The above information is collected and compiled by Shenzhen LCM manufacturer-Xingyuhe Electronics.

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