Galleries / How to Make a Digital Display That Rolls Like a Magazine

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Rachel Cernansky; published May 14, 2009

A Plastic "Web"

A High-Tech Maze

Molded and Cured

View From the Inside

Real-Life Inspector Gadget

One More Step

<p>HP Labs is developing a prototype for a flexible screen that could be used in products from computers to smart phones to e-books. The company says the technology should be available for military use in about two years and for private use shortly thereafter.</p><p>The screen is made using a technology HP calls self-aligned imprint lithography, or SAIL. Traditionally, the circuits behind a screen are produced using a batch process, where a group of displays-in-the-making move together from machine to machine. Instead, SAIL uses a faster roll-to-roll process, where a continuous sheet of flexible material is fed into one end of the machinery and a processed product rolls out the other end, like in a newspaper press. For more detail on the how the flexible screen is made, see <a href="http://discovermagazine.com/2009/may/13-pixels-by-yard-hp-prints-flexible-screens-like-newsprint" target="blank">this recent Future Tech article</a>.</p><p>Pictured here is close to what the final product will look like; this particular model includes a 24-by-38 grid of one-square-millimeter pixels. The sample image is displayed by <a href=" http://www.eink.com/" target="blank">E ink technology</a> and controlled and powered by HP's prototype device, which lies underneath. Production of that back panel is pictured in the following</p>

<p>The shiny plastic surface seen at the top of the image is known as the web; it will be formed into the circuitry that controls the flexible display. It's made of several different films: semiconductor, dielectric, and metal layers, all of which are just a few hundred nanometers thick.</p><p>The web shown here is attached to a plastic substrate and coated with a UV-curable photopolymer.</p>

<p>Here the web runs through the roll-to-roll reactive ion etcher, or R2R RIE. It starts in the upper-right corner and is guided by rollers through the idler in the upper-left corner.</p>

<p>The web passes between the two rollers at the center of the image, where the photopolymer coating is molded by a rubber stamp-like device and then quickly cured by a high-intensity UV light.</p>

<p>From inside the R2R RIE, the copper element applies an electric field to one of the electrodes in order to break down chemically reactive gases, like fluorine, into a plasma. The plasma etches the films and will form the transistors and circuits in the flexible display. </p><p>See <a href="http://discovermagazine.com/2009/may/13-pixels-by-yard-hp-prints-flexible-screens-like-newsprint" target="blank">Future Tech</a> for more detail on the etching process.</p>

<p>The web then passes under a microscope that looks for flaws.</p>

<p>An external view of the wet-chemical etcher, which plays a similar role to the RIE but uses a corrosive chemical instead of chemically reactive plasma. The wet-chemical etcher and the reactive-ion etcher are used alternately throughout the process multiple times.</p>

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