Patent GB-323768-A (GB)
Title: Improvements in and relating to colour-responsive photographic media and surfaces
IPC: G03C1/64
Filed: 1928-09-06
Abstract: 323,768. Martinez, M. Sept. 6, 1928. Colour photography; plates, films, and papers; developing.-A sensitive, surface comprises alloxan or its equivalent and at least one substance which will yield a colour other than red under the action of light. Equivalents of alloxan are substances which yield a red colour when exposed to red light, such as alloxantine, alloxanic acid, murexide, and the compounds dimethylglyoxine and alpha.-benzil-dioxime when used in the form of, or in conjunction with, a nickel salt and in the presence of a ferric salt or oxalic acid or an oxalate or both oxalic acid and an oxalate. Development may be in part by heat. The following examples are stated to give, the results indicated. (1) Alloxan or its equivalent with an excess of a photo-sensitive ferric salt such as ferric ammonium citrate applied in aqueous solution; a red images under red light and a blue image under blue or substantially blue light. (2) Alloxan, mercuric chloride, and oxalic acid applied in aqueous solution; with a ferric salt, this mixture gives blue-black under white or ultra-violet rays, blue under blue rays, violet under violet rays, and red under red rays. (3) An emulsion containing alloxan and ferric ammonium oxalate, and preferably also citric or tartaric acid; a blue image. (4) An emulsion containing alloxan and silver nitrate; a yellow image. (5) A mixture of (3) and (4); blue, yellow, green, and black, under suitable light. Further examples are (6) ferric ammonium oxalate, oxalic acid, mercuric bromide, and alloxan in aqueous solution (7) ferric ammonium citrate, tartaric acid, potassium oxalate, alloxan, and silver nitrate in aqueous solution, (8) a mixture of (6) and (7), (9) a mixture of (a) ferric ammonium oxalate, ammonium oxalate, ammonium molybdate, cobalt chloride, and sodium phosphate in aqueous solution, and (b) mercuric cyanide, mercuric sulphate, urea nitrate, alloxan, #- naphthylamine, and lead nitrate in aqueous solution. The above may be emulsified with gelatine, gum tragacanth, sugar or gum arabic. Transparent or translucent, sheets of material such as celluloid, non-flam cellulose, gelatine or artificial silk may be coated on both sides with the sensitive mixtures. By suitable selection of the sensitive compounds, chemical baths, and wave-length of the printing light, images in one colour only may be obtained. Three such images in three primary colours may be superposed in register to form a subtractive colour photograph. It is stated that the sensitive surfaces may be used to reproduce, in a print from a black-andwhite negative, the colours of the rays which produced the negative. In an example, a coloured band as shown in Fig. 1 is photographed in daylight or equivalent light on to a. panchromatic plate, a negative having a graded silver deposit, as in Fig. 3, being obtained. Figs. 3 and 4 are stated to illustrate the action of this negative as a: filter for sunlight and the result of printing on a surface according to the invention, vertical shading representing red and horizontal shading blue. Fig. 5 illustrates the result of an after-treatment with a dilute aqueous solution of potassium iodide; the thinnest parts of the red and black are changed to yellow, represented by stippling. For example, the surface described in example (9) above is exposed to sunlight under a negative until a blue image appears and is them heated by an electric radiator until red and black appear, or the exposure, to sunlight may be prolonged until red and black appear. By development in an aqueous solution containing sodium thiosulphate, ammonium carbonate, and potassium ferricyanide, the black is fixed but the blue gradually disappears. The surface is then bathed in a solution containing potassium iodide and potassium bromide. Yellow and green appear and on immersion in a dilute solution of hydrogen peroxide the blue re-appears and the print is finally washed in water. The Provisional Specifications state also that salts of the urea group, uric acid derivatives, or uric acid dissolved in nitric acid may replace alloxan to form surfaces sensitive to light or heat rays; that alkaline carbonates and oxalates, double salts of ammonium, and alkaline chromates mav be used with the alloxan; and refer also to sensitive surfaces comprising organic ferric salts in conjunction with salts of other metals and organic matters such as mercury, uranium, and oxalates, citrates, and lactates. Specification 280,252 is referred to.