Polymer for timing layer of diffusion transfer material - subject to beta elimination in alkaline medium gives sharp change from impermeable to permeable state

摘要

Polymer (I) used in timing layer of a photographic diffusion transfer unit, which is subject to beta-elimination in alkaline medium, has units of formula R"-CO-O-CAE-CHDY (in which R" is derived from a 2-5C ethylenically unsatd. alkyl gp. A, D and E are H, Me or Pb but are not all Me or Ph. Y is an activating gp.). The (I) layer passes rapidly from an impermeable to a permeable state after a certain time.