High Contrast Developer Consisting of Ferrous Complexes

Abstract

It was found that ferrous developer containing both aminopolycarboxylic acid such as EDTA and carboxylic acid such as citric acid gave a characteristic curve of high contrast and short toe, and that the exhausted developer could be regenerated by exposing it to UV light.
The developing properties for positive and lith films depended on the concentrations of EDTA and citric acid in the developer and on the pH value. In the absence of KBr, the curve of the highest contrast was obtained when the molar ratios of EDTA and citric acid were, respectively, about 1/3 to one of ferrous concentration at the pH range between 6.5 and 7.5. The development in the lower exposure range was retarded by adding citric acid to the developer. In the developer containing 0.2 mol/l of ferrous ion and 0.067 mol/l of EDTA at pH 7.0, the range of the retardation in the lower exposure range became wider with an increase in the concentration of citric acid until about 0.09 mol/l. However, the excess of citric acid and EDTA accelerated the development in the lower exposure range.
The addition of KBr to the developer retarded the development in the overall exposure range. The optimum pH value of the developer to obtain the highest contrast became higher than that in the absence of KBr.
It was also confirmed that the developer gave a phenomenon of image spreading, and that the exhausted developer could be regenerated by adding 5-10 g/l of citric acid to it and the exposing it to UV light.