P‐13.28: Discussion and Resolution of Compatibility Orientation Schemes for Positive and Negative Liquid Crystals in the Cell Rubbing Process

In the field of TFT‐LCD, the Cell process involves coating a PI film (polyimide material) on the surfaces of TFT and CF substrates respectively, and then inducing the rotation of liquid crystal molecules through Rubbing Process. By applying voltage to the TFT to drive the rotation of the liquid crystal, the display purpose is achieved. Currently, there are positive and negative liquid crystals in the Cell process, each with its unique advantages, and both are applied in actual production. The traditional method is to use their own Masks for positive and negative liquid crystals. To this end, Rubbing process technicians proposed the concept of using a set of Masks compatible with both positive and negative liquid crystals. The biggest development challenge of this technology is the Rubbing Mura problem, that is, to ensure that no Mura problem will occur regardless of whether the long side or short side of the glass substrate is rubbed. Rubbing process technicians identified the risks of TFT and CF surface Marks and drew on Mura improvement experience. They conducted vertical Rubbing deterioration tests on Normal products to further quantify the risks of each Mark. At the beginning of product development, Rubbing process technicians proposed multiple design scheme optimizations for certain Marks at the B9 Rubbing design stage to minimize the impact of Marks on Rubbing Mura as much as possible. At the mass production stage, Rubbing process technicians mapped and matched every defective postion after each flow piece, and carried out multiple tests such as PI coating condition changes, Rubbing condition changes, and material changes. Eventually, they successfully reduced the incidence of Rubbing Mura from over 20% to 0.5%.