Passive-matrix LCDs

Passive Matrix LCD The reahzation of high resolution displays, or even the more simple alphanumeric displays, requires the independent addressing of each pixel. Different matrix techniques have been established common characteristics are the rectangular... 

Supertwlsted nematic displays may be passive-matrix LCDs, containing no active (switching) electronic components. Nowadays much higher performance, especially for colour displays. Is obtained from active-matrix LCDs. In this construction, a thin-film transistor Is added to each pixel to ensure an adequate and constant drive is maintained between refresh cycles. This [Pg.466]

The drive electronics was invented at the beginning of LCD development. The main drive electronics was followed from the passive matrix LCD (PM LCD) to active matrix LCD (AM LCD). Even if the main products moved to active matrix LCDs, the rms-respending characteristics peculiar to nematic liquid crystals remained as the drive electronics progressed. 

Matrix Addressing Technologies for Passive Matrix LCDs... 

There are two major types of LCD displays in use in laptops today active matrix screen and passive matrix screen. Their main differences lie in the quality of the image. Both types, however, use some kind of lighting behind the LCD panel to make the screen easier to view. 

Flat panel displays are a necessary prerequisite for the full visual availability of information. After development of passive matrix displays used in digital watches, calculators [160] and portable computers, intensive work started in the development of large-area, full colour active matrix liquid crystal displays with high resolution. At the present time, LCDs are a major market force rivaling cathode ray tubes [157a],... 

Multiplexed STN LCD on a passive matrix. In order to have one hundred rows, at least how steep must the voltage-transmittance curve be (find the y value defined by Equation (10.6)) ... 

T. Tanaka, Y. Sato, A. Inoue, et al., A bistable twisted nematic (BTN) LCD driven by a passive-matrix addressing, Proc. Asia Display 95, 259 (1995). 

On the other hand, since 1995, active matrix displays have been predominant over passive matrix displaj in the market. Notebook computers with displays from 10 to 13 inches have been the main application for active matrix LCDs. For this application, TN mode displaj have been used and consequently demand for other modes has been limited. FLCs or AFLCs have little chance of being used for this application. 

So far, four display modes have been proposed in ferroelectric and antiferroelectric display applications, as shown in Figure 9.34. A bistable switching in surface stabilized ferroelectric liquid crystals (SSFLCs) has been manufactured as a passive matrix liquid crystal display (PM-LCD). The counterpart of AFLC is a tristable switching, which is also a promising candidate for PM-LCD. In addition to these PM-LCDs, active matrix displays (AM-LCDs) are also proposed in FLC and AFLC materials, i.e., deformed helix FLCD (DHFLC) and V-shaped LCD (VLCD). In this section, PM-AFLCD and AM-VLCD will be described. 

Active-Matrix LCDs. Increase in FPD size along with demand for video response equivalent to the CRT made it necessary to avoid the high level of cross talk between adjacent pixels in passive displays. The nonlinear response of the liquid crystals was no longer suffieient and it became apparent that a switch was needed at each pixel. In principle, several switching technologies could be utilized since they all could be fabricated with films and photolithography. Metal-insulator-metal (MIM) devices, diodes, and transistors have all been tried. Thin-fihn transistors (TFTs) have performed the best and as a result have been adopted for most active-matrix applications. 

There has been a remarkable development in the technology of liquid crystal display (LCD) devices in recent years. The driving method of LCDs can be classified into passive matrix (PM) and active matrix (AM) driving. For example, the former display drive is used in information displays, such as for audio sets in cars or in monochrome clock displays. The development of AM-LCDs came after the practical application of the PM-LCD and goes back to the end of the 1980s. The development of suitable liquid crystal materials occurred in parallel with the development of AM-LCDs. 

Yuet-Wing Li, Li Tan, Fion Sze-Yan Yeung, and Hoi-Sing Kwok, Passive-matrix-driven fleld-sequential-color LCD, 38th Society for Information Display Intenuttional Symposium, Long Beach, CA, 154-157 (2007). 

A reflective contrast of 8 1 at normal incidence was demonstrated. Perfect uniform LC alignment was achieved on both the plastic and glass substrates [50]. To demonstrate the alignment quality on plastic substrates a nine-digit reflective passive matrix TN-LCD mounted in a smart card was fabricated (Figure 4.14). 

Many LCDs are based on active-matrix addressing, in which an active device circuit containing one or more TFTs is connected to each pixel. The TFT circuit at each pixel effectively acts as an individual electrical switch that provides the means to store display information on a storage capacitor for the entire frame time, such that the pixel can remain emitting during this entire time rather than for a small fraction of time, as is the case in passive addressing. 

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