Matrix-type displays addressing

Bistability of a display material does not guarantee multiplexibility. Proper drive schemes must be designed in order to make multiplexed displays on a passive matrix. A good drive scheme should possess the properties of fast addressing speed, low drive voltage, no crosstalk, and a simple waveform. According to the number of phases in the addressing, there are three major types of drive scheme for the bistable TN (1) one-phase drive scheme, (2) two-phase drive scheme, and (3) three-phase drive schemes. 

The most advantageous technology of display production is active matrix addressing. According to forecasts for 1995 the main type of liquid crystal screens used in personal computers, portable TVs, and measuring devices will be based on this technology [1]. We will consider matrix active addressed displays in more detail. 

For driving matrix liquid crystal display panels, the silicon metal-oxide semiconductor field effect transistor (MOSFET) fabricated on a silicon monolithic wafer has been investigated by several groups [134-150]. The MOS transistor circuit fabrication techniques are well developed and have been used to produce various LSI devices. A dynamic scattering mode, a planar type GH mode or a polymer dispersed (PD) mode are used in these displays because the silicon wafer is intrinsically opaque. The circuit configuration of the panel is essentially the same as that of the p-Si TFT switch matrix addressed liquid crystal display panel as shown its equivalent circuit in Fig. 18(a). 

There are two types of matrix addressing schemes— passive and active. The passive matrix (PM) addressing scheme requires the row and coluiim electrodes to address each individual pixel. This scheme still promises well in the area of bistable device such as ferroelectric liquid crystal (FLC) display and bistable twisted nematic (BTN) display because they do not need a control unit for gray-scale capability. The active matrix (AM) addressing scheme is the most developed and widely adopted one in cmrent LC displays. In this scheme, each pixel is cormected to a small electronic switch or TFT made with o-Si, poly-Si, or CdSe. This switch not only enables the pixel to hold the video information until it can be refreshed, but also prevents cross talk among neighboring addressed pixels. 

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