New Convenient Synthetic Route for Photosensitive Poly(benzoxazole)

This review article is concerned with two new convenient synthetic routes for a photosensitive poly(benzoxazole) (PBO). The first synthetic route is based on poly(o-hydroxyamide) and 1-{1, 1-bis[4-(2-diazo-1-(2H)naphthalenone-5-sulfonyloxy)phenyl]ethyl}-4-{1-[4-(2-diazo-1(2H)naphthalenone-5-sulfonyloxy)-phenyl]-methylethyl}benzene (S-DNQ). Poly(o-hydroxyamide) was prepared by polycondensation of 2, 2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and diphenyl isophthalate in 1-methyl-2-pyrrolidinone (NMP) at 185-205°C. The photosensitive PBO precursor consisting of poly(o-hydroxyamide) and 30 wt% S-DNQ showed a high sensitivity (110 mJ cm-2) and contrast (5.0). The second route is based on poly(o-hydroxyazomethine) and S-DNQ. Poly(o-hydroxyazomethine) was prepared by condensation of 2, 2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane with isophthalaldehyde in NMP/toluene under azeotropic conditions. Poly(o-hydroxyazomethine) containing 30 wt% S-DNQ functioned as the positive working photoresist. The positive image was successfully converted to the PBO pattern by thermal treatment.