GB503092A - Improved process of treating sensitive photographic film - Google Patents

Abstract

503,092. Stabilizing photographic emulsions. KODAK, Ltd. (Eastman Kodak Co.) June 26, 1937, No. 14745. Drawings to Specification. [Class 98 (ii)] The sensitometric characteristics, e.g. speed contrast and tendency to fog, of photographic material comprising a cellulosic film support having coated thereon a layer or layers of gelatino-silver halide emulsion are stabilized against change under subsequent storage conditions of varying temperature and humidity by placing it in an environment of such dryness that it reduces the moisture content of such material to the same as that obtained when such material is brought into moisture equilibrium with an atmosphere of ordinary room temperature and pressure, and a relative .humidity of less than 2 per cent, preferably less than À5 per cent, and keeping it in such environment for at least two and a half weeks. The material may be kept in an environment containing calcium chloride, magnesium perchlorate, activated carbon, activated alumina, silica gel or sulphuric acid, or in an environment in which the moisture is removed mechanically as by continually circulating the air through a refrigerating unit, or in a vacuum in which the moisture is removed by pumping. The film may be kept in such environment at a temperature of about 70‹ F. The treatment is especially applicable to film comprising a cellulosic support made by dissolving the basic material in organic solvents and allowing the solvents to evaporate and having between the support and the sensitive emulsion a substratum layer comprising a colloid, e.g. gelatine, which is coated on the support in the form of, a solution with water and other solvents, especially those having a softening action on the support, e.g. acetic acid or acetone. Examples of suitable supports are nitrate and acetate esters of cellulose including mixed esters, such as cellulose acetate propionate or acetate butyrate. The treatment can be applied to films in which several weeks occur between the coating of the substratum and the coating'of the sensitive emulsion and can be applied several weeks after the coating of the emulsion. The treatment is especially applicable to cellulosic film supports coated with silver bromide emulsions not containing optical sensitizers, for example sensitizing dyes, and with emulsions of relatively low sensitivity, fine grain and high gamma and may be applied also to film coated with high speed and sensitized emulsions. Graphs are given showing the effect of storage under varying conditions on speed and contrast of untreated film and film treated for periods of approximately two and a half, five, and nine weeks.