A simple liquid crystal display (LCD) backlight unit (BLU) comprising only a single-sheet polydimethylsiloxane (PDMS) light-guide plate (LGP) has been developed. The PDMS LGP, having micropatterns with an inverse-trapezoidal cross section, was fabricated by backside 3-D diffuser lithography followed by PDMS-to-PDMS replication. The fabricated BLU showed an average luminance of 2878 cd/m(2) with 73.3% uniformity when mounted in a 5.08 cm backlight module with four side view 0.85cd LEDs. The developed BLU can greatly reduce the cost and thickness of LCDs, and it can be applied to flexible displays as a flexible light source due to the flexible characteristic of the PDMS itself.

A polydimethylsiloxane (PDMS) light-guide plate (LGP) having micropatterns with an inverse-trapezoidal cross section was developed for a sheet-less LCD backlight unit (BLU). The micropatterned PDMS LGP was fabricated by backside 3-D diffuser lithography followed by two consecutive PDMS replication processes: photoresist-to-PDMS and PDMS-to-PDMS replications. The fabricated LGP showed an average luminance of 2878 nits and a uniformity of 73.3% in a 2-in. backlight module with four side-view 0.85-cd LEDs. It also could feasibly be applied to a light source for flexible displays owing to the flexible characteristic of the PDMS itself. FIGURE 1 -A schematic view of (a) the conventional BLU with three additional optical sheets and one reflector film and (b) the proposed micropatterned PDMS LGP for sheet-less LCD BLU. Journal of the SID 16/2, 2008 329

This paper presents a new packaging technology that uses a nanoporous columnar thin film to seal microelectromechanical system (MEMS) devices at the wafer level. In the proposed packaging process, the processing temperature is 350 • C. The process is relatively inexpensive compared to wafer level packaging processes, because the wafer-bonding step is eliminated and the die size is shrunk. In the suggested approach, a sputtered columnar thin film at room temperature forms vertical nanopores as etch holes, and an air cavity is formed by the removal of a sacrificial layer through the nanopores in the columnar membrane. Subsequent hermetic vacuum packaging of the cavity is achieved by depositing thin films over the membrane under low pressure. The hermeticity of the packaging was verified by using an optical surface morphology microscope to measure the deflection change of the sealing membrane before and after breaking of the vacuum through an interconnected membrane. The long-term hermeticity was monitored by measuring the maximum central deflection of the PECVD sealing layer over a period of 170 days. The precise pressure (0.7 Torr) and short-term (30 days) pressure change inside the cavity were measured by encapsulated Ni Pirani gauges, representing packaged freestanding MEMS devices.

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