GB788343A - Improvements in or relating to photographic silver halide emulsions - Google Patents

Abstract

788,343. Photographic silver halide emulsions. DU PONT DE NEMOURS & CO., E. I. Jan. 5, 1956 [Feb. 7, 1955], No. 475/56. Class 98(2) 'Two or three component polyamides as described and claimed in Specifications 765,893, 786,344 and 786,345 replace all or part of the normally used gelatin or polyvinyl acetal colloids. Otherwise the emulsion manufacture, including additions as of sensitizing and dispersing agents, hardeners, and colour formers which may be of polyvinyl acetal type follows normal practice. Twelve examples detail the manufacture, thus in Example 1 silver iodobromide is precipitated into an aqueous solution of the copolymer of methacrylamide and N-3-methacrylamidopropyl-N : N- dimethyl-#-aminopropionate betaine made by a method following the procedure of Specification 765,893, ripening is carried out in the presence of excess bromide and ammonia, a large proportion of gelatin is dissolved in the mixture and this is cooled, broken up and washed, remelted, digested with normal additives and coated on a cellulose acetate support an dried. In Example VI the colloid is polymer only, no gelatin, and the acetone precipitation method of manufacture, without water washing, is followed. Most of the examples describe also the preparation of similar emulsions using gelatin only, and indicate that the relative speeds of the copolymer emulsions are about double those of the gelatin emulsions; high speed or "press" negative, or cine positive films usually being produced. Specifications 376,746, 513,471, 537,961, 579.895 [Group XI], 629,482. 631,269, 635,294, 641,368, 652,928, 661,477. 662,793 and 786,346 also are referred to,