Sericol Group Limited

Sericol Limited

Peter Dickinson

Michael Ellwood

Fereidoun Abbasi

Julie E Pratt

Nicholas R Collins

John Hamilton

A photopolymerizable composition for making screen printing stencils. The composition comprises polyvinyl alcohol having at least one photocrosslinkable group appended thereto. At least one metal salt, wherein the metal is selected from: aluminum, zinc, chromium, zirconium, titanium, tin or iron, is added to the composition. The metal salt is used to improve water resistance of a screen printing image that is prepared from the photopolymerizable composition.

Screen printing stencil

Photopolymerizable grafted polyvinyl alcohols including groups of formula ##STR1## wherein n represents zero or an integer from 1 to 6, m represents zero or 1 (with the proviso that m represents zero when n represents zero), Z together with the nitrogen and carbon atoms to which they are attached represent a heterocyclic ring optionally fused to one or more benzenoid or heterocyclic rings, X.sup.- represents an anion, R' represents an alkyl group, and p represents an integer from 1 to 4. Compositions containing such grafted polyvinyl alcohols, for example for screen printing stencils, have shown high sensitivity to light.

Photocurable compositions comprising grafted polyvinyl alcohol derivates

Photopolymerizable polyvinyl alcohols including a group of formula ##STR1## wherein R.sub.1 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, or a hydrogen atom; R.sub.2 represents a substituted or unsubstituted alkyl group, a primary, secondary or tertiary amino group, a cyano, hydroxy or nitro group, a halogen or hydrogen atom or, together with the pyridine ring to which it is attached, part of a quinolyl group; R.sub.3 represents a chlorine or hydrogen atom or, together with the benzene ring to which it is attached, part of a naphthyl group; and X.sup.- represents an anion, and photocurable compositions for producing screen printing stencils including such polyvinyl alcohol derivatives. Compositions of the invention show high light sensitivity with low levels of photocrosslinkable groups grafted to the polyvinyl alcohol.

Photocurable compositions

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

Peter Dickinson