DISPLAY TECHNOLOGY - MATERIALS & TECHNIQUES

Display technology is an evolving field.  On-going development by laboratories and companies is advancing the technology worldwide to meet more demanding requirements. Key properties driving these improvements include a high degree of color saturation, high black-to-white contrast and high spatial resolution. Familiar technologies used in today’s common displays include LCD, LED, OLED and their hybrids.  Future goals include achieving lower power and higher contrast in thin flexible formats.  Also desirable is the ability to operate in high ambient lighting conditions which requires specific architecture.  Currently, imaging displays range in size and application from cell phone-sized electronics to theater screens, video walls, and billboard-scale advertising panels.  Following are some development highlights of display technology.

Phosphor Pixels

Some newer technologies include employing colored solid state diode lasers whose beams are scanned to compose individual RGB pixels. Individual LED RGB pixel arrays compose another display technology. One example of the latest technology [1] is Phosphor pixels that are stimulated by a 405 nm laser diode to emit RGB colors to produce images. The Phosphor pixels grouped as RGB triplets are currently made from powders incorporated as paints. The development of film-layer replacement materials are intended to improve color saturation, contrast and resolution properties.

Electrophoretic Displays

Among the evolving display technologies is a promising form based on electrophoresis.  Electrophoretic displays involve the transport of charged particles, such as ions or microspheres, between two oppositely charged transparent electrodes. The separation of charges can be engineered to produce a medium that can display color and contrast changes in text or images.  The medium can be made very thin as, for example, with “e-paper”, electronic ink and “smart paper.”

The field of electrophoretic image reproduction is relatively recent, and new materials are being investigated and applied in a variety of approaches. Electrophoretic display types include sub-classes defined by materials and pixel-addressing processes. Electrochromic display operation uses the change in the ion environment to modify the optical properties of an ion-supplying liquid. As voltage is applied through the liquid layer between transparent electrodes, mobile ions cause a thin film layer of Tungsten Trioxide (WO3), for example, to reflect or transmit.  The transparency of a window can thus be controlled by changing the applied voltage

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