Fine stripe coating and micro patterning of organic thin films using double nozzles for OLEDs

The aim of this work is to investigate the feasibility of coating and patterning of fine organic thin-film stripes using double nozzles. For fine stripe coating of an aqueous poly (3,4-ethylenedioxythiophene):poly (4-styrenesulfonate) (PEDOT:PSS), we have changed the outer surface of the needle from hydrophilic to hydrophobic in such a way that lateral capillary force is suppressed and thus the PEDOT:PSS stripe becomes narrow. Using a table coater with the hydrophobic needle (inner diameter = 51 μm), we have achieved the 54-μm-wide PEDOT:PSS stripe at a maximum coating speed of 30 mm/s. For micro patterning of PEDOT:PSS thin-film stripes, we have employed double needles; one for discharging the main solvent of the underlying thin film and the other for sucking the dissolved thin film. It is found that the pattern width decreases as the patterning speed increases and the pattern factor (the ratio of film thickness to slope length) is of the order of 10−3 due to the isotropic patterning characteristics. Such a patterning scheme is also shown to remove non-aqueous poly (N-vinylcarbazole) (PVK) films coated in the presence of a bank structure. With the coating and patterning process, we have successfully fabricated multiple OLED stripes, an OLED device with the patterned light-emitting stripe, and OLED pixels, demonstrating its potential applicability to solution-processable OLEDs.