Abstract
Polyimides are well-known for their high chemical inertness and thermal stability. However, it is usually challenging to synthesize UV-curable polyimides since the imidization reaction requires such harsh conditions that acrylate type double bonds cannot withstand. In this work, synthetic methods are developed to obtain polyester-imide type binder polymers with high thermal stability, high compatibility with the other components of the black photoresist, and fine photolithographic patterning property for the negative-tone black photoresist. The syntheses of diimide-diacid or diimide-diol intermediates for the polyesterification with dianhydride gave polyester imides which meets this requirement. The photolithographic tests have shown that the patterning of the micron-sized PDL of the organic light emitting diode (OLED) panel could be obtained. This work will interest the researchers working on the design and optimization of thermally stable binder polymers.
Highlights
Organic light emitting diodes (OLEDs) have become one of the major information displays, especially for the small size mobile displays owing to their lightweight, excellent form factor, wide viewing angle, low power consumption and high contrast ratio [1]
We reported a series of photosensitive polyimide/polyamic acid type binder polymers
In this work we studied a series of new polyester imide type binder polymers, which have two carboxyl and two acrylate groups per repeating unit while containing imide unit in the main chain
Summary
Organic light emitting diodes (OLEDs) have become one of the major information displays, especially for the small size mobile displays owing to their lightweight, excellent form factor, wide viewing angle, low power consumption and high contrast ratio [1]. This binder polymer so-called cardo-binder has been used in the patterning of black matrix (BM) and color filters of liquid crystal display (LCD). It is a polyester type epoxy acrylate containing fluorene moiety. Organosolubility, alkaline developability, chemical compatibility and thermal stability are the indispensable requirements for a qualified binder polymer in the black photoresist for patterning PDL on the OLED panel. Its acidity was provided by phenolic-OH groups This polyimide based binder polymer exhibited higher thermal stability than the commercial cardo-binder but it had slight residue after development [7] [8]. Abbreviations of the compounds are as following: 4,4'-(Hexafluoroisopropylidene)diphthalic Anhydride (6FDA); 5-(2,5-dioxo tetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (MCDA); 4,4'-Biphthalic anhydride (BPDA); trans-4-(aminomethyl) cyclohexanecarboxylic acid (CYAA); glycidyl methacrylate (GMA); fluorene epoxy acrylate (FEA); pentaerythritol triacrylate (PETA); 3,5-Di-tert-4-butylhydroxytoluene (BHT); tetrabutylphosphonium bromide (TBPB); dimethyl acetamide (DMAc); propyleneglycol monomethylether acetate (PGMEA)
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