Radiation-curable high gloss overprint varnish compositions

Abstract

The present invention relates to radiation-curable overprint varnishes for printed substrates based on multifunctional, uncrosslinked, liquid Michael addition resins. The compositions are UV-curable with little or no photoinitiator present.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a continuation-in-part of the provisional application Ser. No. 60 / 564,025, filed Apr. 21, 2004.BACKGROUND OF THE INVENTION [0002] The present invention relates to radiation curable overprint varnishes (OPV). The overprint varnishes are based on multifunctional, uncrosslinked, liquid Michael addition resins formed from the reaction of acrylate monomers, known as Michael addition reaction acceptors (hereinafter “Michael acceptors”) and β-ketoesters (e.g., ethyl acetoacetate), β-diketones (e.g., 2,4-pentanedione), and / or β-keto amides (e.g., acetoacetanilide, acetoacetamide), or other β-dicarbonyl compounds and mixtures thereof, known as Michael addition reaction donors (hereinafter “Michael donors”) that can participate in the Michael addition reaction. The OPV formulations based on the above multifunctional, uncrosslinked, liquid Michael addition resins can be cured under standard UV cure conditions with no photoinitia...

AI Technical Summary

Benefits of technology

[0012] The multi-functional polyacrylate oligomers, from which the varnishes of the present invention are formulated, have dual chemical functionality. That is, they have both acrylic functionality and a labile ketone group that is capable of dissociating to initiate free radical polymerization of the oligomer upon exposure to UV radiation. Final OPV properties can be modified in a number of ways including use of additional or supplementary acrylate materials, using any number of different β-dicarbonyl compounds, or simply varying the stoichiometry of the reactants which comprise the oligomer. Varnishes can be made softer and more flexible with less shrinkage and significantly better adhesion to a variety of substrates. OPVs based on the novel multifunctional acrylate resins of the present invention exhibit excellent gloss, adhesion, flexibility, solvent resistance, scratch resistance, and durability. These coatings may be cured via chemical means, thermally, or by exposure to UV or electron beam radiation.

Problems solved by technology

Systems comprised of traditional monomers and oligomers often have compatibility issues with some of the above additives, making for less formulating options.

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