Oxime Derivatives as Photobase Generators: Their Use for Novel Photo-Crosslinking Systems

Photochemical behavior of 0-carbamoyloximes as photobase generators was investigated in companson with 0-acyloximes. Acetophenone 0-phenylcarbamoyloxime (PCApO) and acetophenone 0- cyclohexylcarbamoyloxime (CHCApO) as 0-carbamoyloximes and acetophenone 0-phenylacetytoxime (PaApO) as the 0-acyloxime were used. In their phototysis at 254 nm , the order of decomposition rate was PCApO> CHCApO> PaApO. In the photolysis of PCApO, aniline, phenylhydrazine, N,N'-diphenylhydrazine, and acetophenone phenyihydrazone were detected and their yields were determined. This result was very different from that of PaApO, because the main product is benzylamine. In the photo-initiated thermal crosslinking of poly(glycidyl methacrylate) films with these photobase generators, they all acted as crosslinkers for the films and the order of activity was CHCApO > PCApO > PaApO. This result was explained by the basicity and the amount of resulting amines. The photochemical behavior of polymeric photobase generators bearing carbamoyloxyimirio (COl) groups was investigated in comparison with those
bearing acyloxyimino (AOl) groups. The former turned into insoluble upon UV irradiation and post-baking increased the degree of insoluble fraction. On the other hand, the latter was soluble after UV irradiation and post-baking induced the formation of insoluble parts. These thermal crosslinking was explained by the association of resulting amino (or hydrazino) groups by a hydrogen bond. Introduction of pendant epoxy groups into the polymeric photobase generators by the copolymenzation of glycidyl methacrylate was not effective for the photo-crosslinking but very effective for the thermal crosslinking by post-baking. Resulting pendant amino (or hydrazino) groups were thought to react with epoxy groups very efficiently.