Sericol Group Limited

Michael Ellwood

Peter Dickinson

The invention provides new compositions which change color on exposure to actinic radiation and contain a photosensitive onium, e.g. iodonium or sulphonium, salt and a dyestuff which changes color when protonated. The compositions may also include a resin, especially a resin curable by the onium salt when the latter is exposed, and preferably an epoxy resin. The compositions are useful especially as coatings, e.g. for making screen stencils or for producing lithographic printing plates.

Photosensitive systems showing visible indication of exposure

Aqueous dispersions comprising water, a cationically curable compound, and a photosensitive onium salt, and preferably other ingredients such as sensitizers, fillers, and plasticizers, are useful for making printing screens, lithographic plates, and printed circuit resists. After exposure, the un-cured composition is easily removed by washing with water.

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Broadstairs, United Kingdom

Michael Ellwood