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Volume: 40 | Article ID: art00013
A New System for Forming High-Contrast Direct-Positive Images
  DOI :  10.2352/J.ImagingSci.Technol.1996.40.1.art00013  Published OnlineJanuary 1996

A very-high-contrast direct-positive image was obtained when a prefogged AgBr photographic emulsion containing certain bipyridinium salts, such as 1-n-butyl-4-(4′-pyridyl)pyridinium bromide hydrochloride (Compound 1), was processed with a developer that contains Metol and ascorbic acid as developing agents. Results of photographic and electrochemical studies suggested that Compound 1 has two functions, as an electron acceptor and as a precursor of a nucleator. A theory was developed that, during exposure, Compound 1 acts as an electron acceptor, which produces a direct-image,and that Compound 1 is neutralized during development to form 1-n-butyl-4-(4′-pyridyl)pyridinium bromide (Compound 2), which acts as a nucleator during development and produces very-high-contrast images.

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Naoki Obi, Kiyoshi Suematsu, Yasuhiko Kojima, Hiroaki Muratake, Yasuo Shigemitsu, "A New System for Forming High-Contrast Direct-Positive Imagesin Journal of Imaging Science and Technology,  1996,  pp 70 - 76,

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Copyright © Society for Imaging Science and Technology 1996
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