Active Matrix LCDs (AMLCDs) generally utilize Twisted Nematic (TN) liquid crystal technology for optical modulation. Simple TN devices have been manufactured in great volumes quite successfully for a wide variety of applications. The application of TN technology should therefore be a straightforward transfer of manufacturing skills to the active matrix technology, simply with a more complex substrate. In fact, there are a number of challenges related to material selections and process technologies. Materials requirements affect not only the performance of the display but have an impact on processing methodology as well. Defects which can result from the manufacturing processes have an impact on Active Matrix displays which is significantly different than on simple TNLCDs. Some process tolerance requirements are much higher for AMLCDs, and the increased information content plays a large role in the manufacturing tolerances. All of these factors mean that making LCDs from Active Matrix substrates is not equivalent to making simple LCDs, yet the yield goals must be even higher because of the cost of the substrates. These challenges and the process requirements for meeting them will be discussed in this paper.
"Challenges of manufacturing LCDs from active matrices", Proc. SPIE 2174, Advanced Flat Panel Display Technologies, (1 April 1994); doi: 10.1117/12.172143; https://doi.org/10.1117/12.172143