Uniaxially Cracked ITO on PET Substrate and its Application in Flexible Displays

Uniaxially cracked indium tin oxide (ITO) on a polyethylene terephthalate (PET) substrate and its application in replacing photolithography to make stripe ITO electrodes were developed. An ITO coated PET (ITO/PET) film uniformly and controllably rolled and uniaxially cracked. This procedure produced fine, parallel cracks in the ITO separated by 5∼10 microns. The crack separation and electrical isolation of the resulting long and thin ITO electrodes was enhanced by etching with dilute hydrogen chloride (HCl) or by uniaxially stretching. Heating and stretching proves the most effective, producing a crack width of about 0.05 microns and a differential conductivity (measured parallel and perpendicular to the cracks) in the resulting films greater than two orders of magnitude. A polymer dispersed liquid crystal (PDLC) shutter was prepared using the cracked ITO/PET film as one substrate. The addressed lines were defined by the contact electrode. The sharpness of the line edges increased as the drive frequency was increased. This PDLC prototype demonstrated how photolithographic etching of ITO or printing of conducting polymer could be replaced by controlled cracking of ITO to produce the line electrodes required for flexible, passive matrix displays and in related flexible electronic applications