Patent GB-592417-A (GB)
Title: Improvements relating to photographic emulsions
IPC: G03C1/28
Filed: 1944-08-03
Abstract: 592,417. Sensitized photographic emulsions. KODAK, Ltd. (Eastman Kodak Co., Carroll, B. H., and Spence, J.). Aug. 3, 1944, No. 14833. [Class 98 (ii)] The spectral sensitivity of a light-sensitive silver halide emulsion sensitized with a cyanine dye is modified by incorporating therein a non- ionic alkoxy aromatic aldehyde of the formula R-(CH=CH)n-CHO, wherein R is an aromatic nucleus having at least one alkoxy group substituted into the nucleus and n is zero or one, e.g. o-methoxybenzaldehyde, anisaldehyde, a dimethoxybenzaldehyde such as the 2: 3- or 3: 5-compound, an o- or palkoxycinnamaldehyde, p-ethoxybenzaldehyde, or piperonal, or by incorporating therein an o-hydroxybenzaldehyde. The cyanine dye may produce a sensitivity maximum in the emulsion at one concentration and at a higher concentration or upon digestion produce a second maximum at a longer wavelength. The aldehyde favours the formation of the second sensitizing maximum and increases the sensitivity at the longer wavelength. Tests for determining the production of a supersensitizing effect and the solubility of the aldehyde in gelatin are described. The aldehyde may be used at concentrations of from 1 to 10 or more grams per litre of emulsion, and may be added before, at the same time as, or after the sensitizing dye. The aldehyde may first be diluted with a water-miscible solvent such as methyl alcohol. More than one aldehyde and more than one sensitizing dye may be added. The emulsion may have a gelatin or other binder, and may be coated on a glass, metal, paper, cellulose nitrate or acetate, or polyvinyl acetate. Dyes specified are 3 : 3<1> : 9-triethylthiacarbocyanine iodide, 3 : 3<1>-diethyl-9-methylthiacarbocyanine bromide, 3: 3<1> - diethyl - 9 - methyl - selenacarbocyanine bromide, 3 : 3<1> - diethyl - 9 - methyl - 4 : 5 : 4<1> : 5<1> - dibenzthiacarbocyanine chloride, 3 : 3<1>-dimethyl-9-ethyl-4 : 5 : 4<1> : 5<1> dibenzthiacarbooyanine chloride, 3 : 3<1> : 9- triethyl-4 : 5 : 4<1> : :'51-dibenzthiacarbocyanine chloride, 3 : 3<1>- diethyl - 9 -phenyl - 4 : 5 : 4<1> : 5<1>- dibenzthiacarbocyanine chloride, 3 3<1>: 9-triethyl-5 : 5<1>-dichlorothiacarbocyanine bromide, 3 : 3<1>-diethyl-9-methyl-5 : 5<1>-dichlorothiacarbocyanine bromide, 3 : 3<1>-dimethyl-9-ethyl-5 : 51- dichlorothiacarbocyanine bromide, 1 : 1<1> di - ethyl-2 : 2<1>-cyanine iodide, 3 : 1<1>-diethyl-4 : 5- benzthia-2<1>-cyanine bromide and 2 : 1<1>-diethyl- 6<1>-methoxythia-2<1>-cyanine iodide. In example (1), 3 : 31- diethyl - 9 - methylselenacarbocyanine bromide and o-methoxybenzaldehyde are added to a fast gelatino silver bromiodide emulsion. In example (2), 3 : 3<1>-diethyl-9-methylselenacarbocyanine and 2 : 3-dimethoxybenzaldehyde are added to a similar emulsion. In example (3), 3 : 6<1>-dimethyl-1<1>-ethyl-4-phenylthiazolo- 21-cyanine iodide and o-methoxybenzaldehyde are added to a similar emulsion. In example (4), 3 : 3<1> - diethyl - 9 - methyl - 4 : 5 : 4<1> : 5<1> - dibenzthiacarbocyanine and o-methoxybenzaldehyde are added to a, similar emulsion. In example (5), 3 : 3<1>-diethyl-9-methylselenacarbocyanine bromide and salicylaldehyde are added to a similar emulsion. Specifications 498,290 and 515,372 are referred to.