Aqueous negative resist based on gelatine

In the presence of catalytic iron salts, it is possible to photochemically induce a negative crosslinking of gelatine. Coated substrates are for this purpose exposed and briefly swivelled in diluted hydrogen peroxide solution which acts as crosslinking agent. Non-exposed areas can subsequently simply be rinsed off with warm water. The obtained structures are thermally stable up to about 250°C and only marginal colour changes are observed upon intense heating. A removal is easily possible with diluted sodium hydroxide solution. A major advantage of gelatine resists is their good environmental tolerability, since organic solvents can be omitted completely. The resist is suitable for applications in photovoltaics and for solvent-free processes.