Rewritable Paper Thin LCD Is Flexible, Light and Tought

Consequently, optically rewritable LCDs are thinner than traditional LCDs, at less than half a millimeter thick, can be made from flexible plastic, and weigh only a few grams. “It’s only a little thicker than paper,” said Jiatong Sun, a co-author from Donghua University in China.

Optically rewritable LCDs are durable and cheap to manufacture because of their simple structure. Moreover, like an electronic paper screen in an e-book, energy is only required to switch display images or text. Therefore, running costs are low because these new LCDs don’t need power to sustain an image once it is written on the screen. 

Combined flexible blue optically rewritable LCD

Credit:  Zhang et al.

The second innovation involves the spacers that create the separation of the plastic or glass plates. “We put spacers between glass layers to keep the liquid crystal layer uniform,” Sun said. Spacers are used in all LCDs to determine the thickness of the liquid crystal. A constant thickness is necessary for good contrast ratio, response time and viewing angle. However, when plates bends, it forces the liquid crystal away from the impact site and leaves sections of the screen blank and so alterations in spacer design are critical to prevent liquid crystal in flexible LCDs from moving excessively. Developing a flexible design that overcomes this barrier has proven challenging.

The researchers tried three different spacer designs and found that a meshlike spacer prevented liquid crystal from flowing when their LCD was bent or hit. This innovation enabled them to create the first flexible optically rewritable LCD.

An additional innovation involved improved color rendering. The scientists report that until this study, optically rewritable LCDs had only been able to display two colors at a time. Now, their optically rewritable LCD simultaneously displays the three primary colors. They achieved this by placing a special type of liquid crystal behind the LCD, which reflected red, blue and green. To make this into a commercial product, Sun wants to improve the resolution of the flexible optically rewritable LCD.

“Now we have three colours but for full colour we need to make the pixels too small for human eyes to see,” Sun said.

Contacts and sources:
Julia Majors

Citation: A flexible optically re-writable color liquid crystal display. Authors: Yihong Zhang, Jiatong Sun, Yang Liu, Jianhua Shang, Hao Liu, Huashan Liu, Xiaohui Gong, Vladimir Chigrinov, Hoi Sing Kowk. Applied Physics Letters, 2018; 112 (13): 131902 DOI: 10.1063/1.5021619