New Design for Self-Developing Imaging Systems Based on Thermally Labile Polyformals

The polycondensation of bis-allylic or bis-benzylic diols with dibromomethane under phase transfer catalysis may be used to generate some polyformal polymers and copolymers which depolymerize readily when heated or when subjected to acidolysis. The polymers are best prepared by condensation of diols such as 1,4-dihydroxy-2-cyclohexene or 1,4-dihydroxy-1,2,3,4-tetrahydronaphthalene and CH2Br2 under phase transfer conditions. The polymers which are obtained by this process generally have fairly broad polydispersities and are stable to temperatures higher than 150°C. Under acid catalysis, they decompose below 80°C to afford mainly the aromatic elimination product (benzene or naphthalene), and formaldehyde hydrate. As the polymers absorb very weakly even in the deep-UV (Emax < 300), imaging is possible through formulations incorporating both the polyformals and a small amount of a triarylsulfonium salt or similar photoacid generator. The polyformals can be used as self-developing and chemically amplified imaging systems which operate in the deep-UV and possess good sensitivities due to the catalytic nature of their photoinitiated thermal decomposition.