Sericol Group Limited

John R Curtis

John D Renwick

Peter E Heaton

The invention provides photosensitive compositions useful in the production of screen printing stencils which comprise, in addition to the usual ingredients, also an indicator to show when a layer formed from the said composition has been isolubilized by exposure to actinic light.

Process of preparing screen stencil using diazo photosensitive

Aqueous compositions useful in making stencils for screen printing by the direct, indirect or direct/indirect method comprise a photopolymerizable monomer, a water-insoluble photoinitiator, a tertiary amine accelerator, a water-soluble colloid, water, and a water-miscible organic solvent.

Photopolymerizable composition for producing screen printing stencils

Aqueous compositions useful in making stencils for screen printing comprise a solution of an unsaturated prepolymer dispersed in an aqueous solution of a colloid, and a photo-initiator. Such compositions may be coated on suitable support sheets to produce photosensitive sheets useful for making stencils for screen printing by the direct, indirect, or direct/indirect methods.

Photopolymerizable materials for use in producing screen printing

The invention provides novel thioxanthone photoinitiators having the formula: ##STR1## wherein R.sub.1 alkyl, alkoxy, alkylthio, halogeno, nitro, amino, alkyl-amino, di-alkyl-amino, hydroxy alkyl-amino, alkanoylamino, benzoylamino, N-alkanoyl-N-benzoyl-amino, sulphonamido, or acetyl, R.sub.2 is alkylene, A is --COOH, --SO.sub.3 H, --OSO.sub.3 H, or --O--CO--X--COOH (where X is such that HO--CO--X--COOH is a di- or tri-carboxylic acid of up to 8 carbon atoms), n is 0, 1, or 2 and m is 1 or 2, provided that when A is --COOH, m is 2, the aforesaid alkyl, alkoxy, alkanoyl, and alkylene residues containing up to 4 carbon atoms each, as the free acid or as a salt thereof. The photoinitiators may advantageously be used in water-based photopolymerizable compositions, e.g. for use in screen stencil production.

Water soluble thioxantone photoinitiators

Aqueous compositions useful in making stencils for screen printing comprise one or more unsaturated monomers, a tertiary amino compound, a colloid, and a water-soluble, carboxy- or sulpho-alkyleneoxy-thioxanthone photoinitiator. When coated on to a suitable support sheet and dried, photosensitive sheets are obtained useful for making stencils for screen printing by the direct, indirect, or direct/indirect methods.

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Thanet, United Kingdom

John R Curtis