Details:
Summary:
A brief summary will initially be given, of the different types of photosensitive materials which have been used over the years in solvent-developed negative plates. This will be followed by a description of subsequent advances which enabled the use of water/solvent mixtures as developers. The push toward eliminating solvent from the developer altogether, continued and a resume of the state of the art will be presented. The two main chemical approaches for achieving total aqueous development, namely the use of diazo resins and the use of photopolymerizable unsaturated materials, such as acrylates, will be discussed in full. Particular emphasis will be place on a novel approach to aqueous development pursued by Howson-Algraphy. The approached is based on the use of a difunctional monomer which has both a vinyl polymerisable double bond and separately, a second reactive group. The chemistry of either functionality can be exploited independently without affecting the latent utility of the other group. This duality of function has enabled novel, light-sensitive diazo polymers of varying properties and varying molecular weights, to be synthesized. Groups with hydrophilic or hydrophobic character can be basic groups and even photochromic groups can likewise be incorporated. In essence, an aqueously developable, light-sensitive coating can be chemically, rather than (as in the past) physically assembled.