Since Tang reported their first double-layer green thin-film organic electroluminescent device with high efficiency and low driving voltage

organic light-emitting diode (OLED) displays have led to intense activity around the world for this new display technology due to its lots f promised advantages over existent display technologies. Most research and development has expanded to the device emitting mechanisms and new organic materials but several researches on the OLEDs fabrication process. Since OLEDs are the sandwich structures of one or several organic materials between two electrodes

they can be integrated in a passive matrix (PM) addressed display by patterning the anode in columns and the cathode in rows. The key process of PMOLED substrate is the fabricating cathode separator pattern by photolithography process.The image reverse technique for substrate separator includes coating

pre-baking

exposing with photomask

reverse baking

and flood exposing. The photoresist (PR) AZ5214 was coated on glass substrate with etched ITO film patterns by Delta30bm coating machine

and then pre-baked by Delta300bm. The photolithograph machine is Karl-Suss MA6. At last the substrates with cathode separator pattern were used to fabricate organic device to test the separator performance.When PR were uniformly exposed under UV light

strong optical absorption by the photo active compound (PAC) in the PR films

and as the PAC is destroyed

this absorption is removed as well

so the upper layer PR is exposed before the bottom layer. The development of photoresist can be considered a surface-rate limited etching reaction. The parameters that control this rate are resist and developer chemistry (held constant) and the PAC concentration of the photoresist at the surface exposed to the developer. The exposing model and developing model can be connected by PAC concentration and the shape of developed PR can be simulated.The main factors effecting reverse taper shape were thickness of photo-resistance

exposure and reversal bake. SEM test shows the reverse trapeziform shape of separator section with 45°obliquity and photoresist thickness 3μm. Optimum parameters about preparation cathode separator were obtained

coating rotation speed 1200r/min

pre-bake 100℃/90s

exposure time 0.8s

reversal bake 125℃/45s

flood exposure time 5.5s

developing time 40s.