Silver halides photolysis

Also included are some of the chemical and physical steps which immediately follow the initial interaction of silver halide materials with fight The story of these imaging processes would not be complete without them and they serve to illustrate the diverse applications of the common photochemical process of silver halide photolysis. 

Before we look in detail at the core photochemical process of silver halide photolysis and the amplification of the photochemical response resulting from chemical development we will first explore the early history of imaging technology. By doing so will introduce the essential elements of modern photographic systems. 

We start the discussion of the group (2) of photo-de-diazoniations in imaging processes by noting that, after silver halide photography, systems based on the photolysis of diazo compounds form the second most important group of imaging processes. 

Many photographic products are based on the photolysis of silver halides. These materials are especially suitable for use where short exposure times are needed. Thus, high speed photographic films are manufactured for use in cameras. Also, coatings of silver halide on paper are utilized in the on-line production of colour reflection prints where rapid passage through an exposure device is necessary. 

Dry-Film Resists Based on Radical Photopolymerization. Photoinitiated polymerization (PIP) is widely practiced in bulk systems, but special measures must be taken to apply the chemistry in lithographic applications. The attractive aspect of PIP is that each initiator species produced by photolysis launches a cascade of chemical events, effectively forming multiple chemical bonds for each photon absorbed. The gain that results constitutes a form of "chemical amplification" analogous to that observed in silver halide photography, and illustrates a path for achieving very high photosensitivities. 

Photochemical Decomposition of Solids. Defect ionic solids frequently undergo photochemical degradation on absorption of quanta of appropriate energy. The formation of the latent image in silver halides and the photolysis of sulphides and oxides in moist air are of this class. 

The understanding of the basic mechanism of photolysis of silver halide is incomplete yet vital for the planning and interpretation of experiments. This fact is illustrated by the ramifications inherent in the contemporary discussions of the latent image in silver halide. There are the conventional Gurney-Mott mechanism (1) and the thermodynamic model ((5,9). We have described the Gurney-Mott model. The thermodynamic view envisages nucleation of a supersaturated concentration of silver atoms in silver halide as induced by light. Obviously the effect of external variables is quite different in the two mechanisms. 

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