Digital full color displays

One of the most obvious markets for thin-film vapor-deposited organic materials is in flat panel displays [123], a market currently dominated by LCDs. Over the last two decades, a great improvement in the lifetime and efficiency of OLEDs have been achieved. OLED displays can already be found in simple applications such as automobile stereos, mobile phones, and digital cameras. However, to exploit the advantages of the technology fully, it is necessary to pattern the OLEDs to form monochrome, or more preferentially, full-color displays. This section will consider the difficulties involved in addressing such displays (either passively or actively) and the variety of patterning methods that can be used to produce full-color displays. 

Liquid crystal display systems have been increasingly used in electro-optical devices such as digital watches, calculators, televisions, instmment panels, and displays of various kinds of electronic equipment, ie, lap-top computers and word processors. The dominant reason for thek success is thek extremely low power consumption. Furthermore, the Hquid crystal display systems have been remarkably improved in recent years, and today they have high resolution (more than 300,000 pixels) and full color capabiUty almost equivalent to those of a cathode ray tube. 

FIGURE 7.16 A commercially available digital camera containing a full-color AMOLED display from Sanyo-Eastman Kodak. 

When a paper display is needed or when textual information is to be printed, as in a report, it is common to use a digital printer such as a laser jet or inkjet printer. These devices are inexpensive and provide 600 to 2400 dots per inch, more than adequate for most applications. The laser jet devices use an electrostatic transfer of black toner material to paper to form the desired image, which is then fused to the paper by passage over a heater. Color versions are available but are more expensive because they require three toner cartridges, one for each of the primary colors. The inkjet printers use movable solid-state heads with many fine holes through which small droplets of ink are ejected by selective localized heating behind the orifices. The ink is drawn by capillary action from a reservoir chamber and, by use of three primary colors, full-color images can be printed at up to 2400 dots per inch. 

All of these were given in Table 6-2 of the last chapter. More recently, digital technology has replaced this type of CRT using long decay phosphors. A computer-controlled display utilizing a full color CRT has been developed for aircraft traffic control. Therein, the direction, size of target and altitude of aircraft are directly displayed upon the phosphor screen. 

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