Patent GB-636144-A (GB)
Title: Improvements in or relating to light-sensitive photographic elements
IPC: G03C1/58
Filed: 1947-08-29
Abstract: Photographic material comprises at least one layer composed of a hydrophilic polymeric colour former having one or more p light-sensitive diazonium salts uniformly dispersed therethrough. A self-supporting foil may be made by coating a solution of the colour former and diazonium salt on to a smooth surface, drying, and stripping off.  The solution may also be coated on to a permanent support, e.g. paper, or a solution of the colour former may be coated on to a support and dried, and the dried layer then impregnated with a solution of the diazonium compound.  Organic (preferably water-miscible) solvents, many of which are specified, or aqueous-organic solvents, may be used.  Hydrophilic hydroxyl colour formers are preferably used, and colour-forming nuclei capable of forming azomethine or indophenol dyes may be attached to recurring carbon atoms of the polymer chain through carbonamide, sulphonamide, amino, acetal, ether or acetal linkages.  The polymer chain should contain more than 200 carbon atoms, and it is preferable that for every 100 chain atoms 1 to 25 colour former nuclei should be present. At least 1 aliphatic OH group should be present for every 8 carbon atoms in the chain, and preferably 1 to 2 OH groups for every 5 chain atoms.  The hydroxyl polymer that may be connected to colour former nuclei may be a hydrolysed polyvinyl ester (e.g. polyvinyl alcohol), a hydrolysed interpolymer of a vinyl ester (e.g. acetate, propionate, or butyrate) with an olefine (e.g. ethylene, propylene, or butene-1), or polymers of other vinyl compounds (e.g. acrylic acid, an acrylic or methacrylic alkyl ester, or vinyl chloride or cyanide), or polymers of maleic anhydride, or a partial ester, ether, or acetal of such polymers.  The colour former nucleus may be a phenol, naphthol, acylacetarylide, cyanacetarylide, b -keto-ester, pyrazolone, N-homophthalylamine, coumaranone, indoxyl, or thioindoxyl nucleus. Numerous amines from which the diazo compound may be prepared are specified.  The solution may also contain an anti-foaming agent (e.g. decyl, dodecyl, or tetradecyl alcohol) when applied by spraying, a metal deactivator (e.g. a water-soluble metal nitrite, an alkyl nitrite, or an alkyl or aryl phosphate) when coated on metal (e.g. ferrous metal), a pigment (e.g. white such as titanium dioxide or barium sulphate, green, or yellow) complementary in colour to the final azo dye image, and the usual additions e.g. urea, thiourea, allyl thiourea, or thiosulphate, and/or compounds forming double salts with diazonium compounds (e.g. Sn, Zn, or Cd salts of weak acids such as tartaric, citric, succinic, or boric acids).  The support may be metal, plastic, glass, waterproofed paper, or a cellulose derivative or superpolymer (e.g. nylon) or other transparent film base.  Templates may be cut from exposed and processed metal or composition board carrying the light-sensitive composition.  In example 1, baryta - coated paper is coated with an aqueous-ethanol solution of m-(1-hydroxynaphthalene-2-sulphonamido)-benzaldehyde polyvinyl acetal, and an aqueous solution of the zinc chloride double salt of diazotized p-aminodiethylaniline is applied to the dried layer.  The exposed material may be developed with ammonia vapour.  In examples 2 and 3, the colour former is m-[p-(5 - ethylcarbonato - 3 - methyl - 1 - pyrazolyl) - benzamido]-benzaldehyde ethylene glycol acetal of polyvinyl alcohol and m-(benzoylacetamido)-benzaldehyde polyvinyl acetal respectively.  Specifications 535,341, 593,088, 598,477, 627,125, 627,353, 635,294 and 6367/46, (as open to inspection under Sect. 91), are referred to.