Patent GB-500717-A (GB)
Title: Improvements in colour photographic elements and processing thereof
IPC: G03C7/30
Filed: 1937-05-10
Abstract: 500,717. Colour photography. KODAK, Ltd. May 10, 1937, No. 34976/38. Convention date, May 9, 1936. Divided out of 500,826. [Class 98 (ii)] Material having three differentially colour sensitive silver halide emulsion layers superimposed on a single support and having between two adjacent layers or surrounding the middle layer or in one of the outer layers an ultraviolet absorbing substance resistant to developing baths or to developing and mild oxidizing baths or to developing and fixing and mild oxidizing baths is colour processed by developing all the latent images to silver and exposing the residual silver halide of the layer containing or overlying the ultra-violet absorbing substance only by means of ultra-violet light. The element contains a colourless ultra-violet absorbing substance such as aesculine, quinine, anethol, triphenylmethane, cuniarone, acetaminoquinoline, hydroxy quinoline sulphonic acids, hydroxynaphthoic acids, naphtholsulphonic acids, naphthylamino sulphonic acid and anthracene substitution products. The substance, if acidic, may, precipitated in gelatine be inorganic or organic bases, for example basic dyes such as auramine, acridine yellow, benzoflavine, and thioflavine ; if basic, by diazo light yellow 2G, di-(p-aminobenzoyl)-alpha-naphthylaminesulphonic acid and anthraquinonesulphonic acid or by phosphotungstic, silicotungstic and phosphomolybdic acid or their salts or reduction products. The three-layer material may comprise an upper blue-violet sensitive layer, a middle yellow and green sensitive layer, and a lower red sensitive layer. The filter layers surrounding the middle layer are composed of strongly swelling gelatine. A yellow filter may be placed between the upper and middle layers, and the use of green or redorange filters between the middle and lower. layers is referred to. The red filter-dye, if used, is water-insoluble or non-diffusing. Insoluble filter-dyes may be precipitated in the gelatine or incorporated in a highly dispersed state. Water soluble substantive and colloidal dyes or insoluble salts of soluble dyes, may be used. The lower emulsion is infra-red sensitive. The red-sensitive emulsion may be sensitized with 4 : 4<1>dichloro-2 : 2<1>-8-triethylthiacarbocyanine chloride. The blue-sensitive emulsion may be coloured yellow to serve as a filter, and either the yellow emulsion or the yellow filter layer or an additional colourless gelatine layer may contain the ultra-violet absorbing substance. The ultra-violet absorbing substance may be introduced after exposure by bathing. In modifications the three-layer material may comprise an upper blue-violet sensitive layer, a middle red and orange sensitive layer, and a lower yellow and green sensitive layer, or may comprise an upper red sensitive layer, a middle yellow-green sensitive layer, and a lower blue sensitive layer. After exposure the material is developed in a non-tanning neutral developer such as ferrous oxalate, amidol, or diamido-o-cresol. Organic developers in solutions containing sodium-carbonate may also be used. Colour sensitivity may be partially restored after development by treatment with an alkali sulphite or bisulphite. The three layers may be saturated in a strong solution of the developing agent and development effected by treatment with weak alkaline solutions. Concentrated developing solution may be allowed to diffuse into all the layers at a low temperature and development started or accelerated by warming. The middle layer may have ultra-violet impermeable filters on both sides, and the residual silver halide of both upper and lower layers is made developable with ultra-violet light. The middle layer can be developed even without light action by onergetic colour developers. The residual silver halide may first be converted to silver chloride in a fine state of subdivision. Material comprising a red or red and orange sensitized lower layer, a middle yellow and green sensitized layer, and a colourless or yellow ultra-violet absorbing layer between the upper and middle layers is developed, the lower. layer exposed to red light and developed blue-green, and the middle layer exposed to ultra-violet light through the lower layer and developed purple, or the upper layer is exposed to ultra-violet light, and the middle purple image is obtained (a) by development after destroying residues of the latent images in the other layers with ammoniacal potassium ferricyanide with a colour developer containing ammonia, alkali, alcohol, or acetone, or with an alkaline leuco-vat dye solution preferably containing alcohol or acetone, both of which act without exposure ; (b) by removing all reduced silver, destroying the filter dyes by oxidation or acid, exposing the middle layer' on both sides to white, blue, or ultra-violet light or to soft X-rays, developing purple, and removing the silver with Farmer's reducer; (c) by removing all reduced silver, destroying the filter-dyes by oxidation or acid, reducing the residual silver bromide of the middle layer without exposure with vigorous ordinary developer or with an organic or inorganic reducing agent, converting to highly dispersed silver chloride with mercuric chloride and colour developing without exposure ; (d) the middle layer is exposed to ultra-violet light or soft X-rays through the silver in the lower layer and developed ; (c) the silver-bromide of the middle layer-is converted into silver iodide or one of its complex salts and coloured purple or blue-green by dyes which can be made insoluble by phosphotungstates, and the silver is removed ; (f) the silver chloride of the middle layer may be converted to silver ferrocyanide which may be converted to nickel dimethylglyoxime or titanium ferrocyanide, which-latter compound may be dyed with blue basic dyes, or alternatively the silver ferrocyanide may be converted to non-tanning mordants and coloured purple or blue-green by basic dyes, and removed, if desired, after insolubilization of the dyes. The support may be of cellulose acetate or regenerated cellulose, and may contain or be coated with colourless ultra-violet substances. An ultra-violet filter layer may be on each side of the middle layer, the top and bottom layers may be successively exposed to ultra-violet light and colour-developed, and the middle layer intensively exposed on both sides to soft X-rays or ultra violet-light (after removal of the filters) and colour developed, the silver being then removed. 'The top layer may be coloured yellow with nitrosodimethylaniline. If the silver is first removed, the middle layer may be exposed to white or coloured light. Material having an upper ultra-violet filter and a lower orange-red filter may be used and the lower layer exposed to blue light, the upper.to ultra-violet light, in either order, -and the middle layer then processed. With an upper yellow filter and a lower ultra-violet filter, the lower layer is exposed to ultra-violet, the upper to blue light. The material may have a middle red-sensitized layer. If the ultra-violet absorbing substances are resistant to developing, fixing, and mild oxidizing, baths, all the images may be developed to silver, fixed, reconverted to silver halide and processed. In a three-layer material in which the middle layer is surrounded by colourless ultra-violet absorbing substances or by a colourless ultra-violet absorbing substance and by a yellow filter, the silver images are, after fixing, reconverted to silver chloride and bromide and independently made developable and redeveloped. In a modification of the material for printing purposes the lower layer is not specialty colour sensitized, only the middle layer being colour sensitised. The middle emulsion or all three emulsions, may be of silver chloride. Black- and-white colour component negatives may be printed on the material. The ultra-violet absorbing substances may be left in the finished picture. The middle layer may be sensitized with yellow-green sensitizers, such as erythrosine, and rhodamine Band 6G, stable to mild oxidizing-agents, and may then be exposed to yellow-green light and colour developed prior to processing of the outer layers. Multicolour or lenticular screen images, bipack images or three separate colour component images may be printed on to the material according to the invention. Specifications 376,746, 498,875, 500,720, 500,793, 500,795, 500,826, and 501,003 are referred to.