GB697190A - Photographic film having enhanced herschel effect susceptibility and the process of preparing the same - Google Patents

Abstract

697,190. Photographic film. GENERAL ANILINE & FILM CORPORATION. April 12, 1951 [April 18, 1950], No. 8543/51. Class 98 (ii). A photographic film comprises a support, a light-sensitive orthochromatic silver halide emulsion carried thereby, and at least one water-permeable colloid layer in contact with the emulsion layer and having uniformly dispersed therein, in desensitizing amount, a desensitizing compound. Numerous desensitizing compounds are specified, including Pinakryptol Green, Pinakryptol Yellow, anthraquinone-2- carbonic acid, anthraquinone-2-sulphonic acid, and phenosafranine. The colloid coating may also contain glycerol, a hardener such as formaldehyde, glyoxal, or potassium chromium alum, and a wetting agent such as saponin, isopropylnaphthalene sulphonate, or sodium dioctyl sulphosuccinate. The colloid layer may be provided both as an undercoat and an overcoat, and the emulsion layer may be coated in two or three layers each separated by a colloid layer. The film may be used in reflex or ordinary contact printing, and in the latter case may bear an antihalation layer. The binder for the colloid layer may be gelatin, a water-soluble cellulose derivative such as hydroxyethylcellulose, a polyvinyl alcohol containing a gelling agent, a polyvinyl acetaldehyde acetal resin, or a partially hydrolysed polyvinyl acetate resin. The support for the film may be a simple or mixed cellulose fatty acid ester, cellulose nitrate, a cellulose ether, a fusible water-insoluble synthetic linear super, polymer, polyvinyl chloride, bromide or acetate- or a copolymer of vinyl chloride and vinyl acetate or bromide, or a mixture thereof. In example 1, a film coated with an orthochromatic type gelatino silver iodobromide emulsion is overcoated with a gelatin solution containing saponin, glycerol, potassium chromium alum, and Pinakryptol Yellow. In example 2, a film is successively coated with an aqueous gelatin solution containing phenosafranine, saponin, and potassium chrome alum, and with the emulsion of example 1. In example 3, a film is successively coated with the emulsion of example 1, an aqueous gelatin solution containing Pinakryptol Green, formaldehyde, and saponin, and with a further layer of the emulsion of example 1. In example 4, the film of example 4 is provided with an initial undercoating layer of the desensitizing coating and with a final similar overcoating. The film may be used to remove images of black lines and letters in the production of colour separation negatives in which the black lines have been removed by fogging the emulsion, contactprinting a negative of the subject on to the film, and partially developing. A blue-separation positive is made on film which has been given a slight fogging by successive contact printings using blue and red filters. A redseparation negative is made on film which has been strongly fogged, also by two successive contact printings. The separation prints are further printed on to high-contrast photomechanical film.