By rubbing in one direction with a flannel on the alignment film, an alignment layer of the LCD liquid crystal panel can be formed. The liquid crystal molecules at the alignment layer will be arranged in parallel according to the rubbing direction, so that a uniform alignment can be obtained.
The orientation of the liquid crystal molecules at the top and bottom of the two wafers is 90 degrees, which is the central link of the twisted nematic (TN) liquid crystal cell. The principle of rubbing orientation has been debated so far, but one thing is certain, that is, when the liquid crystal molecules are arranged along the rubbing direction, the energy of the system is the lowest, or the liquid crystal molecules at the alignment layer tend to be arranged along the direction of the smallest energy. This energy is called anchoring energy.
As for the micro-mechanism of the friction giving the alignment direction, it can be mainly considered from the following two aspects: First, the dense and shallow grooves with different widths are formed through friction.
The ends of the groove are not the same. If analogy is made with the process of sizing, the groove is one end wide and deep, and the other end narrow. Such a groove, in particular, a groove (nanometer scale) equivalent to the size of the liquid crystal molecules, necessarily exerts an effect on the alignment of the liquid crystal molecules. Another consideration is the effect of the alignment direction of the organic polymer of the alignment layer material on the orientation of the liquid crystal molecules.