Technology

How to Make a Digital Display That Rolls Like a Magazine

Computer screens of the future may wrap around your finger. Here’s an inside look at how HP makes their prototype model.

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Photo Credits: by Rachel Cernansky; all photos courtesy of Hunter Freeman

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.

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 this recent Future Tech article.

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 E ink technology and controlled and powered by HP's prototype device, which lies underneath. Production of that back panel is pictured in the following

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.

The web shown here is attached to a plastic substrate and coated with a UV-curable photopolymer.

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.

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.

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.

See Future Tech for more detail on the etching process.

The web then passes under a microscope that looks for flaws.

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.

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