Patent GB-768436-A (GB)
Title: Improvements in photographic light sensitive emulsions
IPC: G03C1/043
Filed: 1955-04-22
Abstract: 768,436. Photographic emulsions. KODAK, Ltd. April 22, 1955 [April 29, 1954], No. 11641/55. Class 98(2) A'photographic silver halide emulsion of which the' light-sensitivity has been increased by the incorporation therein of an alkylene oxide polymer or derivative thereof (e.g. a polyalkylene glycol, or a condensation product of an alkylene oxide with a glycol, phenol, aliphatic alcohol, aliphatic amine, aliphatic acid. or a hexitol ring dehydration product, the alkylene oxide preferably containing from 2 to 4 carbon atoms and the polymer having a molecular weight of at least 300), is stabilized by the incorporation of parabanic acid. Addition of the parabanic acid lowers the pH of the emulsion to about 4.8, but neutralization of the acid before the addition or of the emulsion after addition reduces the antifogging effect. The addition does not affect the hardening action of mucochloric acid, a - hydroxy - adipaldehyde or 1 : 5 - bis - (methanesulphonoxy) - pentane, but interferes somewhat with the hardening action of formaldehyde and glyoxal. The polyalkylene oxide (polyalkylene glycol) used may be derived from ethylene, propylene or butylene oxide. Condensation products of ethylene oxide with long chain alcohols should have a molecular weight of about 700, while other derivatives may have a molecular weight of 1500 to 4000 or more. The emulsion may be additionally sensitized by digestion with naturally active gelatin or by the addition of sulphur, ruthenium, rhodium, palladium, iridiuni, platinum, or gold compounds or of reducing agents such as stannous salts, polyamines such as diethylenetriamine or spermine of bis - (# - aminoethyl) - sulphide or its water-soluble salts. The emulsion may be optically sensitized with cyanine or merocyanine dyes or both, and may be stabilized with the mercury compounds of Specifications 742,219, 742,221 or 742,224. The parabanic acid may also be incorporated in a colloid (gelatin). layer contacting the emulsion. In Example 1, speed, gamma and fog data before and after incubation are given for a silver bromiodide emulsion which has been digested with a sulphur compound as disclosed in Specification 235,211 [Class 98(2)] and potassium chloraurate, chemically sensitized with polyethylene oxide oleyl ether, and panchromatically sensitized; portions of this emulsion are tested with no further addition and with varying amounts of parabanic acid. In Example 2, similar data are given in respect of an emulsion which has been chemically sensitized with sulphur and gold compounds as in Example 1 and optically sensitized with 3 : 3<SP>1</SP>' - diethyl - 9 - methylthiacarbocyanine bromide; portions are tested with no further addition, and with the addition of polyethylene oxide lauric ester, oleyl ether, ether of glucose monolaurate, lauric acid amide, and phenyl ether with and without, in each case, parabanic acid. Specifications 380,431, 380,851. 443,559 [all in Group III], 548,019, 592,676, 600,058, 602,158, 602,160, 618,061, 636,140, 658,592, 661,645, 663,019, 664,230, 680,593, 682,355, 729,345 and 755,369 also are referred to.