GB750494A - Improved method of producing photographic images constituted by precious metal - Google Patents

Abstract

750,494. Physically developed mercury photographic images. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. March 25, 1952 [March 28, 1951], No. 7650/52. Class 98 (2). In producing photographic images by physical development with a salt of a metal more electropositive than antimony and a reducing agent of a mercury image formed in an exposed lightsensitive layer comprising at least one lightsensitive compound the light-reaction product of which is capable in a wet medium of setting free mercury from mercurous ions introduced into the layer either prior or after exposure, prior to or simultaneously with the formation of the mercury image there is introduced into the layer an anion which is capable of reducing the concentration of free mercurous ions to such an extent that the sensitivity of the layer is raised by a factor of at least two, said anion not precipitating mercurous salts. The sensitivity of paper or superficially saponified cellulose acetate foils which are sensitized with 1- hydroxy 2-diazo 6-methyl benzene 4-sulphonic acid and mercurous nitrate and are physically developed in a bath containing metal, citric or tartaric acid and silver nitrate is increased by the addition of sodium lactate, together if desired with silver nitrate, during sensitization or after exposure but before development. Alternatively sodium lactate may be added to a similar foil sensitized with 1-hydroxy 2-diazobenzene 4-sulphonic acid either during sensitization or after exposure but before development when the foil is bathed in a solution of mercurous nitrate and nitric acid. The same diazo compound may be incorporated in a foil with mercurous oxide and sodium citrate. In the case of foils sensitized with 1-methoxy benzene 4-sodium diazosulphonate which are treated after exposure with a bath containing mercurous nitrate and nitric acid, and sodium lactate or sodium acetate or a bath containing mercurous nitrate, lactic acid and sodium lactate. In further examples cellulose acetate foils sensitized with o-nitro mandelic acid nitrile in ethanol are treated after exposure but before development with mercurous nitrate, nitric acid, and sodium lactate, and foils sensitized with the mono-sodium salt of 1-diazo 2-hydroxynaphthalene 4.6-disulphonic acid, mercurous nitrate and nitric acid are treated after exposure but before development with sodium lactate. Dye-forming physical developers may be used, a red image being produced by the action of a bath consisting of a mixture of an aqueous solution of 4-amino phenylamine nitrate, tartaric acid, and silver nitrate with an ethanol solution of 1.5-dihydroxy naphthalene, and a blue image being produced by means of a bath consisting of a mixture of an aqueous solution of 4-dimethylamino phenylamine nitrate, lactic acid, and mercurous nitrate with an ethanol solution of α-naphthol, the mercury image being bleached out with potassium ferricyanide followed by washing with hypo. Specification 748,1,72 is referred to.