Development of Low Temperature Curable Positive-Tone Polyimide Materials for Organic Electro Luminescence Displays

Low temperature curable photosensitive polyimides for insulation layers and planarization layers of organic electro luminescence display were developed to fulfil the seven indispensable requirements; (1) positive-tone photosensitivity, (2) thermal stability (low out gassing), (3) curable at less than 250 °C, (4) low tapered angle, (5) high and stable dielectric strength, (6) excellent adhesion to substrates and (7) chemical resistance to photo-resist stripper treatment. The above seven requirements were achieved by the design of photosensitive compounds consisting of the polyimide precursor polymer, diazonaphtoquinone sulfonate and the cross-linker that actively caused the cross-linking reaction at less than 250°C. In the case of the photo-resist stripper treatment, the film thickness change could be controlled by the optimization of the polymer/cross-linker ratio. And the 5% weight loss temperature of the positive-tone photosensitive polyimide material containing the cross-linker reached 383°C using 250°C cured film.