The main attributes of the various passive matrix LCD technologies are summarized in Table 4.1. Diagonal size is limited by the size of the glass used in manufacturing; most manufacturers now have the capacity to produce up to a 17-inch diagonal. The number of vertical lines achievable depends on the multiplexing ratio; most FSTN panels are addressed as two panels so that a 480:1 multiplexing ratio results in a 960-line LCD. Ferroelectric LCDs are limited in a different way; since the effect is bistable, an unlimited number of lines can be addressed. The switching time, however, limits the number of lines if video response is required. For example, if the switching time is 50 micro sec, a 500-line LCD can be refreshed in 25 msec and a 1000-line LCD in 50 msec. Response time of the LCD is listed as the on time plus off time; this represents the best metric for portable computer use. The quality of color refers to the saturation and range of colors achievable (active matrix LCDs would earn a grade of excellent). Viewing angle quality is listed for single-user applications such as personal computers or personal TVs. Cost estimates are based on available data for the units in production and guesses for those not in production.

The main competition for passive matrix LCDs is the active matrix LCD; Table 4.2 compares the two types of LCDs. As Table 4.2 shows, active matrix LCDs win in almost every category except cost. It is the high cost of active matrix LCDs that limits their widespread use today.

Table 4.1
Comparison of Various Passive Matrix LCDs

Table 4.2
Comparison of Passive and Active Matrix LCDs

Published: June 1992; WTEC Hyper-Librarian