Ciba-geigy Ag

John A Clark

David W Butcher

Alan Adshead

James Doyle

Multicolor holograms using gelatin as the binder and having interference fringes lying in layers parallel to the substrate, the colors of which are visible by reflection in incident natural light, by treating the holographic material which has been holographically exposed and processed to produce a hologram therein, by applying to the selected areas of the gelatin which contains the interference fringes a solution of a compound which causes the interference fringes to separate permanently and produce a bathochromic shift in the replay wavelength.

Multicolor holograms using gelatin as the binder and method for

A method of preparing a hologram which comprises subjecting holographic material to a holographic exposure, the holographic material comprising silver halide emulsion of which at least 80% by weight of the halide is bromide, developing the exposed material in a silver halide developing solution to yield developed silver, converting the developed silver to silver chloride using a bleaching agent selected from ferric ions, persulphate ions, chlorate ions, peroxides and water-soluble quinones, in the presence of chloride ions and then fixing out the silver chloride using a silver halide fixing agent which dissolves silver chloride but not silver bromide or silver iodobromide under the conditions of use.

Method of preparing a hologram

A method of preparing a hologram which comprises subjecting holographic material to a holographic exposure, the holographic material comprising a silver halide emulsion of which at least 80% by weight of the halide is bromide, developing the exposed material in a silver halide developing solution to yield developed silver, converting the residual silver bromide, in the main part at least, to silver iodide by use of an aqueous iodide solution, removing the developed silver but leaving the silver iodide either by use of a bleach/fix bath under controlled conditions or by rehalogenating the developed silver to silver bromide or chloride using a brominating or chlorinating silver bleach solution and simultaneously or subsequently fixing out the thus formed silver bromide or chloride using a fixing agent under such conditions that silver iodide is not dissolved from the material.

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Altrincham, United Kingdom

John A Clark