Ultraviolet-cured printing inks

A. S. Deutsch, R. Dennis, and R. Gumbinner, Ultraviolet Curing Printing Inks Having Improved Shelf Life, U.S. Pat. 4,129,486, Dec. 12, 1978. 

Practical Aspects. The foregoing theoretical relationships are difficult to apply to the curing of ultraviolet light-cured printing inks for several reasons. First, the polymerization kinetics of the complex monomers and prepolymers used in flie ink formulations have not yet been investigated under conditions that can be correlated with theory (i. e., low concentrations of reactants, constant temperature, simple model formulations). Second, the ultraviolet light-cured inks are polymerized in bulk to high conversion tiie polyfunctional nature of the... 

Ultraviolet Electron Beam Curing Formulations for Printing Ink, Coating and Paints, 3 Vols., SiTA Technology, London, 1991. 

The use of solventless inks avoids the emission of solvents during drying. The development of such inks has been a major goal of the printing ink industry for the past several years and has resulted in tiie development of several different types 1. ultraviolet light-cured inks ... 

Ultraviolet Light-Cured Inka Ultraviolet light-cured inks are a distinct d rture from conventional printing inks in that fiieir mechanism of... 

Theoretical Aspects. Ultraviolet light-cured inks are cured by free radical-initiated vinyl addition polymerization. The photochemical initiation of vinyl polymerization has been the subject of many investigations dating back more than 30 years, to the first systematic studies of polymerization kinetics. Photochemical initiation offered a reproducible source of radicals that is not dependent upon temperature as is the thermal decomposition of free radical initiators. However, despite these early studies of its mechanism and kinetics, only recently has photochemical initiation become of practical interest, mainly because of the recent development of ultraviolet lamps suitable for production curing of printing inks and coatings. 

The UV technology alluded to above holds out the promise of even more superior labels. In this process, ultraviolet cured inks are used as the printing medium. These are cured by exposure to industrial type UV mercury vapor lamps in either a non-inert system (air environment) or in an inert (oxygen-free) system. The result is excellent adhesion to vinyls, polyesters, polycarbonates, butyrates and acetates and a cured elongation of between 20 and 40% to avoid embrittlement of the substrate. Initial testing has exhibited little sign of degradation and excellent chemical resistance after three years of exterior exposure. Such UV labels as well as other techniques should be considered whenever use demands extended label performance. 

Ultraviolet curing (or UV curing) n. (1) Conversion of a wet coating or printing ink film to a solid film by the use of ultraviolet radiation. (2) The process by which certain polymers or coatings are cured, with the aid of a photoinitiator, by exposure to ultraviolet radiation. One such polymer system is the oligomer tris(2-hydroxymethyl) isocyanurate triacrylate with an initiator... 

The main disadvantage is that web temperatures of 275-325° F are required to cure the film. These temperatures affect the paper properties adversely, and therefore higher-quality, more-expensive paper must be used. Even so, blisterii or cracking in the folder may be a problem. Moreover, the solvent emission, although reduced significantly, is not eliminated, and, as with the ultraviolet light-cured inks, paper printed with these thermally-catalyzed inks cannot be recycled in the currently used processes (8, 9). 

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