Precision ink jet printing of polymer light emitting displays

Precision ink jet printing of organic polymer light emitting diodes relies strongly on the accuracy of the droplet generation process. First of all, the requirements for layer thicknesses of the different layers of the light-emitting stack are tight and consequently all droplets count. The print head does not run at a fixed frequency, but shows a duty cycle of alternately a burst of droplets at high frequency during a short time followed by a time interval during which the print head runs idle. The present paper analyses theoretically the start-stop behaviour of a print head and the consequences of such a duty cycle on the total droplet volume deposited.