Ultrasonics Enable Non-ITO Liquid Crystals

Ultrasound has been used to replace ITO in LCD displays, by researchers in Japan.

ITO is formed using rare metals such as indium. It is not only costly, it is also rigid. The display industry has been searching for a replacement for years, and the latest development comes from a joint research effort by the Tokyo Institute of Technology, Doshisha University (Kyoto) and the Precision and Intelligence Laboratory (Yokohama).

In a traditional LCD display, electrical fields are created using ITO to control LCD molecule alignment. The Japanese researchers, however, have used acoustic fields generated by ultrasound. The system also has the benefit of no moving parts. They created a prototype ultrasonic LC cell, with a thickness of 5-25µm and two ultrasonic lead zirconate titanate transducers.

A flexural vibration mode was exerted on the cell by the transducers. The acoustic radiation forces the LC layer to change its molecular orientation, which of course alters its light transmission capabilities. By modulating the ultrasonic driving frequency and voltage, the researchers can change the spatial distribution of the LC molecules. This enables them to control the distribution of the transmitted light intensity.

The research was published in Applied Physics:

Ultrasonic liquid crystal cell: (a) photograph and (b) configuration. The liquid crystal layers were fabricated with thicknesses of 5, 10 and 25μm