Patent GB-811153-A (GB)
Title: Improved photographic process
Inventor: GAZZARD EDWARD GEORGE
IPC: G03C1/053
Filed: 1956-03-13
Abstract: 811,153. Photographic silver halide emulsions. IMPERIAL CHEMICAL INDUSTRIES Ltd. Feb. 25, 1957 [March 13, 1956], No. 7813/56. Class 98(2). A photographic silver halide emulsion contains an epoxide which is added to the emulsion at any stage of its preparation. The binder of the emulsion, with which the epoxide is said to react, may be gelatin or a gelatin substitute such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose or "grafted polymers" such as those used in Specification 793,549. Many epoxides are specified including monoepoxides such as styrene oxide, cyclohexene oxide, epichlorohydrin, 2; 3 - expoxypropyl methacrylate, phenyl 2; 3 - expoxypropyl ether, 2 ; 3 - epoxypropyl benzoate, 2 ; 3 - epoxypropyl N-phenylcarbamate, ethyl # - phenyl - glycidate and #; # - epoxy - # - phenylpropio - phenone, polyepoxides including diepoxy butane, diepoxy - 2 ; 5 - dimethylhexane, methyl di - (2 ; 3 - epoxypropyl) acetate, dioxides of divinyl benzenes, 4 - vinyl - cyclohexene dioxide, diepoxycylohexane, and glycidyl ethers of polyhydric alcohols and phenols, glycidyl amines and esters of polybasic acids, containing two or three 2 ; 3 - epoxypropyl groups, and epoxy polymers derived from unsaturated epoxides such as described in U.S.A. Specifications 2,765,296 and 2,604,457. The emulsion may comprise a dispersion or suspension of photosensitive granules prepared as in Specification 718,404 or 750,201, followed by dehydration with anhydrous sodium sulphate as in Specification 743,946, adding a petroleum fraction and separating and drying the precipitated product. In Example 1, aqueous ammoniacal silver nitrate is run into an aqueous gelatino solution of potassium iodide and bromide containing phenol. The grafted polymer described in Example 1 of Specification 793,549 is dissolved in water together with caustic soda, the pH adjusted to 7 or 8 with sulphuric acid and the solution added to the silver halide dispersion. The mixture is run into aqueous sulphuric acid to precipitate the gelatine and graft copolymer emulsion. The dried emulsion is dispersed in ethyl lactate and a solution of m - di - (2 ; 3 - epoxypropoxy) - benzene or 2 ; 2 - di - (4 - (2 ; 3 - epoxy propoxy) phenyl) propane in methanol and ethyl lactate is added. The mixture is then coated on baryta paper which has been coated with gelatine or ethyl cellulose. In Example 2, the silver halides are precipitated in the presence of a gelatine graft co-polymer and the emulsion precipitated with sulphuric acid. The dried emulsion is then treated with an epoxide as in Example 1. In Example 3 a gelatino silver bromiodide emulsion is twice precipitated with anhydrous sodium sulphate, and the solid precipitate mixed with aqueous methanol. The emulsion is then warmed with a solution of epichlorohydrin in methanol and ethyl lactate and the mixture coated on a paper base. In Example 4, photosensitive granules containing ethyl cellulose and gelatin (made by adding chrome alum to a warm gelatino silver bromodide emulsion, then adding ethyl cellulose, homogenizing, dehydrating with sodium sulphate, adding petroleum decanting and drying the solid) are mixed with the grafted polymer of Example 1 of Specification 793,549 in methanol and ethyl lactate and a solution in the same solvents of m - di - (2 ; 3 - epoxypropoxy) benzene is added. The mixture is coated on a paper base subbed with ethyl cellulose.