Patent GB-578968-A (GB)
Title: Improvements in the printing of sound records on films
IPC: G03C5/14
Filed: 1943-12-13
Abstract: 578,968. Photographic imbibition - printing processes. KODAK, Ltd. Dec. 13, 1943, No. 20844. Convention date, Dec. 22, 1942. [Class 98 (ii)] A method of reproducing a sound-track consists of foiming a photographic relief image of the sound, treating it with an organic compound which will reduce silver salts or silver oxide, transferring the relief image of the organic compound to a mordanted imbibition blank and reacting it with a silver salt or silver oxide to form a silver sound image at the points of transfer. Hematoxylin, gallein or gallin are the preferred organic reducers, but hydroxy-flavones, e.g. quercetin and quercitrin, tannins, tannic acid, gallic acid, alizarin dyes; poly-hydroxy anthraquinones, e.g. anthragallol, or reducing aldehydes, are also mentioned. In one example, a cellulose ester support carrying an unhardened gelatine-silver halide emulsion layer suitable for forming a relief image, is exposed to a colour separation negative carrying the sound image, the image portions hardened and the unhardened gelatin washed out. The film is dyed with the minus colour and treated on the sound-track by means of a roller or by edge dipping, with a solution of an organic compound, e.g. hematoxylin. The film is pressed on to a chrome alum mordanted gelatin blank and the blank then treated for five seconds in a 5 per cent solution of sodium bisulphite, rinsed and placed in ammoniacal silver nitrate solution. The sound image is neutral gray. In further examples, the gelatin blank is further mordanted with sodium hydroxide and cupric chloride, followed if necessary by treatment in a 1 per cent solution of sodium perborate. Other suitable mordants are compounds of aluminium, chromium, copper, iron, nickel, cobalt, titanium, zirconium, tin, lead, zinc, cadmium, antimony, manganese, bismuth, uranium, tungsten, molybdenum, thorium, vanadium and cerium. The silver salt may be ammoniacal silver nitrate, nitrite or sulphite. In a further example, silver phosphate is formed in the imbibition blank by successive immersions in disodium phosphate, calcium acetate and silver nitrate, the blank receiving the hematoxylin image being afterwards cleared of silver phosphate by treatment with sodium thiosulphate. Silver oxide may be used instead of silver phosphate, being deposited by successive immersion in solutions of a silver compound and potassium hydroxide. The sound relief image can be used for making numerous transfers by treating the film with an aqueous solution of ferric chloride, potassium citrate, sodium sulphite, citric acid and sodium thiosulphate, dyeing appropriately and treating the sound-track with gallein, formamide, sodium hydrosulphite and glacial acetic acid in solution before transfer to the silver phosphate imbibition blank. In a further example, the film is treated with a solution of hematoxylin and formamide, the latter removing dye from the sound-track, and the imbibition blank is mordanted with chrome alum and treated with silver oxalate or silver halide.. After the transfer, the blank is treated with ammonia vapour or an alkaline solution to produce a silver image ; the residual silver salt being removed by sodium thiosulphate. If the silver compound is silver oxide or silver phosphate quinzarin-2-sulphonic acid in alkaline solution may be used as the reducer.