Material and Cell Parameters Considerations in a Highly Multiplexing TN Liquid Crystal Display

The LC material and cell parameters influence on such electro-optical characteristics as the steepness γ, viewing angle dependence β and threshold voltage Vth in a twisted nematic (TN) cell has been investigated. The results have indicated the following: (1) The steepest or smallest γmin at some optimal cell thickness d 1 is reasonably estimated exclusively from the elastic constant ratio k 33/k 11 of LC material. (2) The steepness γmin at the cell thickness d 1 is linearly decreased or definitely improved with decreasing the ratio k 33/k 11. (3) The viewing angle dependence p has a maximum or the worst value at another cell thickness d 2 and is effectively improved with decreasing the cell thickness d in the region d < d 2. (4) The threshold voltage Vth is reduced with decreasing d in the region below another cell thickness d 3, which is different from d 1 and d 2. Through the optimization of LC material and cell parameters based on the above results, a 12-inch diagonal highly multiplexing dot-matrix TN LCD with 640 × 200 pixels has been successfully developed, which displays sophisticated graphic patterns as well as 25 lines by 80 characters with good legibility.