Active Matrix Addressed Displays

1 Thin Film Diode and Metal-Insulator-Metal Matrix Address [1-20] 

The simplest way to overcome the scanning limitations encountered in passive matrix liquid crystal display panels is to provide one or more nonlinear circuit elements at the intersection of the gate and data electrodes, thus producing sharper threshold characteristics for each pixel. Presently, diodes and intrinsic nonlinear devices are used for these nonlinear circuit elements. 

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. 

As for the TFT version, it requires polysilicOn (p-Si) or hydrogenated amorphous silicon (a-SI H). The latter type is a leader, since it allows films over the large area to be formed at relatively low temperatures ( SOO °C). The cost of the process is relatively small and the conventional photolithography technique can be used. TFTs made with this material tend to have excellent leakage characteristics. One of the problems is achieving high drive currents. This is difficult due to the low mobility jjl 0.5 cm /V s) of the material, but nevertheless a-SI TFT active matrices are manufactured in large quantities for actively addressed liquid crystal displays [3]. 

Increasing the display size I requires larger active matrices with a higher number of pixels, which results in an exponential growth of a number of defects, such as broken dots and lines, disconnections, shortages, etc. At the same time the operation characteristics of each nonlinear element must be more stable and reliable. All this leads to a sharp increase in the price of the large area active matrix displays. 

To complete the subject, we have to specify the requirements to liquid crystal materials for active matrix displays. They include  

Though all the listed requirements are important, the most valuable one includes a high degree of purity or low conductivity a that provides the desired time of the charge relaxation Trei via a liquid crystal pixel (Fig. 8.1) in the frame period 

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Kaneko E Active matrix addressed displays Handbook of Liquid Crystals Vol 2A. Low Molecular Weight Liquid Crystals led D Demus, J Goodby, G W Gray, H-W Speiss and V Vill (New York Wiley-VCH)... 

In the present set of experiments, with 0.75 mm wide ITO lines, the sudden increase in resistance and the well-defined, propagation controlled critical failure strain is obtained. In many applications in electronics industry significantly smaller details are present. For active matrix addressed displays, for instance, transistors and connection lines significantly smaller than 100 pm are applied. When the size of the cracks, initiated for instance around a defect, have a stable size, comparable to the size of the component, crack initiation-controlled mechanisms and not the propagation control may govern the resistance of the lines. 

The advent of STN displays and cheaper active matrix addressed displays took over this market, although it has been considered several times subsequently for other market sectors, but without a product being made. 

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