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Thin films enable next-generation displays



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You've finished working on your computer and you're ready to call it a day. Instead of logging off and folding the screen down over a laptop keyboard, imagine rolling up the computer screen and stashing it in your bag. Roll-up computer screens and other flexible light-emitting displays that conform to almost any shape or surface may one day be realities thanks to a team of scientists at Pacific Northwest National Laboratory.

The researchers have developed two key technologies--the Flexible GlassTM engineered substrate that provides a flexible surface on which to build a display and the BarixTM thin film coating that protects a display from harmful air and moisture. These technologies offer the display industry the design flexibility of plastic and the barrier protection of glass.

Because it prevents moisture vapor or air from passing through, glass--durable but rigid--has been the substrate used in both traditional liquid crystal displays (LCDs), such as cell phones and digital watches, and next- generation displays such as organic light-emitting diodes (OLEDs), which offer wider viewing angles, quicker response times and more ruggedness.

One challenge to manufacturing thin, flexible, and lightweight OLEDs was finding a way to make a flexible surface, such as plastic, also impermeable to air and moisture vapor, which quickly destroy an OLED display. The BarixTM coating provides this protection. It also enables the manufacture of thinner displays with fewer potential failures at seams and joints by eliminating the bulky packaging required when using a glass substrate.

The BarixTM coating is made of extremely thin layers of transparent ceramic barrier material deposited with alternating thin polymer (plastic) layers. The layering is repeated until the desired resistance to water vapor and oxygen permeability is achieved. The nanoscale inorganic layers (of less than 50 nanometers) sandwiched between the polymer layers (of less than one micron) produce composite structures that are flexible enough to be rolled yet still prevent air and moisture vapor from passing through. The BarixTM coating is typically less than two microns thick. A human hair, on average, is 100 microns thick.

The Flexible GlassTM engineered substrate is a transparent, flexible plastic sheet that blocks air and moisture but allows light to be transmitted, making it extremely useful in manufacturing sensitive organic electronic devices. Vacuum deposition techniques are used to deposit thin-film layers of nanoscale organic and inorganic materials in multi-layer stacks directly onto a substrate such as polyester film. Each stack is typically less than two microns thick. Display manufacturers can use the Flexible GlassTM product as the substrate on which to build either OLED or plastic LCD displays. After the device is fabricated on the barrier substrate it can be hermetically sealed using BarixTMencapsulation or another sheet of Flexible GlassTM barrier material.

Both Flexible GlassTM and BarixTM technologies have been licensed to the Battelle spin-off company, Vitex Systems Incorporated, for commercialization.

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