In October 1999, Eastman Kodak and Sanyo Electric jointly announced the development of a high quality, 2.4 inch diagonal Full Color active matrix Organic Light Emitting Diode (OLED) display. This technology demonstration resulted from the successful integration of Kodak's organic electroluminescence display technology and Sanyo's low temperature polysilicon TFT technology. Commercial samples are expected to reach the market in 2001. The active matrix OLED displays feature a wider viewing angle and a faster response speed than conventional LCDs. With its low power consumption, high brightness and thin design, these OLED displays when incorporated in digital cameras, personal digital assistants (PDA), videophones and other portable imaging devices, will offer a superior value proposition to consumer electronics products. Several OLED display designs are under development now to serve various market segments. This paper will summarize the status of active matrix full color OLED display development, the key technical challenges, and the path ahead.
The influence of grain boundaries and intragrain defects on poly‐Si thin‐film transistors (TFTs) was investigated by examining the crystallinity of poly‐Si films formed by solid phase crystallization (SPC) and excimer laser annealing (ELA), and the electrical characteristics of transistors fabricated on the poly‐Si films were examined. The increase in grain size by SPC improves field effect mobility (μFE) due to the increase in the emission current over the potential barrier height at the grain boundary. The decrease in intragrain defect densities by an oxide thinning process improves the μFE, threshold voltage (V
th) and subthreshold voltage swing (S). On the contrary, in spite of the small grain size of 800 Å, poly‐Si TFTs fabricated by ELA exhibit good characteristics with a high μFE, low V
th and low S, and good uniformity. It is found that since the realization of excellent performance and good uniformity in poly‐Si TFTs depends on a low trap state density at the grain boundaries and a low intragrain defect density, poly‐Si films formed by ELA are well suited for the application to poly‐Si TFT liquid crystal display with peripheral integrated circuits.
Field sequential color LCDS require an LC‐mode with a fast response time. For this purpose, we have studied an OCB Optical Compensated Birefringence mode that is capable of displaying a gray‐scale with high‐speed response. However, this mode exhibits a splay alignment at initial state. It requires transition from the splay alignment to bend alignment before drive, while it takes a relatively long time in general. To solve this problem a new method is proposed. It employs an optimized TFT‐array structure with a low‐temperature p‐Si TFT‐LCD and a high DC voltage is applied to a common electrode at initial state. This new method enable the initial transition to be less than 3 sec and no defective pixel remains.
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