Emerging Display Technologies

Bringing Back Print by Eliminating the Paper

28 March 2018
Optically-rewritable LCD. Source: Zhang et al.

Want to bring back print? Try paper that doesn’t grow on trees.

That’s the promise of a new, paper-thin liquid crystal display (LCD) that could be used to display a daily newspaper — and be refreshed with news updates throughout the day, eliminating one of the most problematic aspects of traditional media: It goes out of date nearly as fast as it rolls off the press.

Made by optoelectronic engineers in China and Hong Kong, the new LCD is flexible, thin, light, tough — and should be cheap to produce (costing perhaps five dollars for a 5-inch screen).

A conventional LCD uses a liquid crystal filling between two plates, separated by spacers. Electrical connections on the plates create fields to switch individual pixels from light to dark. The new LCD draws upon two key innovations: optically-rewritable LCDs that employ special molecules to coat the plates that hold the liquid crystal, where they will realign in the presence of polarized light; and a mesh-like spacer design that allows the liquid crystal to stay put even if the display is bent.

The optically-rewritable design eliminates the need for traditional electrodes and reduces bulk, allowing displays to be made from flexible plastic with a thickness of less than half a millimeter — not much thicker than a standard sheet of paper. Running costs are also low because energy is only required to switch display images — not to sustain images once they are written on the screen.

Although previous optically-rewritable LCDs had only been able to display two colors simultaneously, the addition of a special type of reflective liquid crystal allows the new device to display all three primary colors. According to Jiatong Sun, a study co-author from Donghua University in China, the resolution will still need to be approved to make the device a commercial product.

"Now we have three colors, but for full color we need to make the pixels too small for human eyes to see," Sun said.

The new optically rewritable LCD design was reported recently in the journal Applied Physics Letters.

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