Toru Hanada

Plastic substrate technologies for flexible displays

A novel plastic substrate for flexible displays was developed. The substrate consisted of a polycarbonate (PC) base film coated with a gas barrier layer and a transparent conductive thin film. PC with ultra-low intrinsic birefringence and high temperature dimensional stability was developed for the base film. The retardation of the PC base film was less than 1 nm at a wavelength of 550 nm (film thickness, 120 μm). Even at 180 °C, the elastic modulus was 2 GPa, and thermal shrinkage was less than 0.01%. The surface roughness of the PC base film was less than 0.5 nm. A silicon oxide (SiOx) gas barrier layer was deposited on the PC base film by a DC magnetron reactive sputtering method. In addition, a unique organic-inorganic hybrid material is coated on the SiOx to further improve the gas-barrier performance. The water vapor transmission rate of the film was less than 0.05 g/m2/day at 40 °C and 100% relative humidity (RH), and the permeation of oxygen was less than 0.05 cc/m2•day•atm at 40 °C and 90% RH. Indium Zinc Oxide optimized for the plastic substrate was deposited on the other side of the SiOx film by the DC magnetron sputtering method. The transmittance was 87% and the resistivity was 3.5×10-4 ohm•cm.