Highly Refractive and Photosensitive Polyimide

Abstract

A highly refractive sulfur-containing photosensitive polyimide (PSPI) based on the PI from 4,4'-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA) and 4,4'-thiodianiline (SDA), 4,4'-methylenebis[2,6-bis(methoxymethyl)phenol] (MBMP) as a cross-linker, and (5-propylsulfonyloxyimino-5H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile (PTMA) as a photoacid generator has been developed. The matrix polymer showed high transparency in the g-line region and the high reflective index of 1.7452 and low birefringence of 0.0081. The PSPI consisting of the PI (84.8 wt%), MBHP (11.0 wt%), and PTMA (4.2 wt%) exhibited the high sensitivity (D_0.5) of 36 mJ/cm² and good contrast (γ_0.5) of 5.1, respectively, producing a clear negative-tone line-and-space pattern with 8-μm resolution.