US2336902A - Photographic material for color photography - Google Patents

Description

Dec. 14, 1943. G 2,336,902

PHOTOGRAPHIC MATERIAL FOR COLOR PHOTOGRAPHY Filed March 19, 1941 RED sENsITIvE LAYER {GREEN SENSITIVE LAYER L BLUE SENSITIVE LAYER-DYED YELLOW f I LAYER RENDERED OPAQUE WHITE DURING PROCESSING T \I'CELLULOID SUPPORT DIRECTION OF EXPOSURE l 12 uentor Patented Dec. 14, 1943 I PHOTOGRAPHIC MATERIAL FOR COLOR l PHOTOGRAPHY Alan"Gilbert Tull, Purley, England, assignor to Latta Syndicate Limited, London, England, a

British company Application March 19, 1941, Serial No. 384,181

. In Great Britain March 27, 1940 4 Claims.

'The present invention relates to the production of color photographic records which are to be viewed by reflection similarly to a paper print.

While it is possible to secure a color photographic record to a paper support to form a refiection print, this is not always convenient or satisfactory particularly when the expsure is made through a Celluloid or other transparent base and the original exposure material is processed to a natural color photograph, since the latter must be viewed from the emulsion side to obtain correct lateral rendering of objects and in that case the thickness of the base separates the colored parts of the record from the reflective paper surface and interferes with correct viewing of the picture. I

In accordance with the present invention the aforesaid difficulties are overcome by the provision of a layer in front (in the direction of passage of the light during the exposure), of the silver halide coat in which the colored image or images is/are produced,. which layeris initially transparent but can be rendered opaque white or other desired light tint during the processing.

Such layer may contain, for instance, zinc hydroxide which is formed in colloidal suspension in a gelatine medium and can beconverted to an opaque white, insoluble zinc compound during the processing. For instance, treatment in sodium carbonate solution will convert'the zinc hydroxide into zinc carbonate. Potassium ferrocyanide will convert it into zinc ferrocyanide, while a soluble sulphide will form zincsulphide, all of which zinc salts are insoluble white compounds. Alternatively the layer may contain another metal salt such as lead sulphate or iodide, or calcium phosphate produced in situ in colloidal form, which is converted into lead carbonate or calcium carbonate in a sodium carbonate solution. A layer containing lead iodide is of yellow color and this fact may be advantageous in some cases as it enables the layer to act as a filter layer also.

In the processing of color photographic records, development in a solution containing sodium carbonate is well known and it will be appreciated that such a solution will efiect conversion of the zinc hydroxide or other substance into an opaque white deposit. Also in some processes, such as those disclosed in my co-pending applications Serial Nos. 378,301 and 378,302, (now Patent No. 2,320,109 of May 25, 1943), filed February 10, 1941, treatment solutions containing potassium ferrocyanide are used and 'such a solution would produce zinc ferrocyanide.

It will be appreciated that it may be unnecessary to use a separate conversion stage for the production of the opaque white layer, while, on the other hand, it may be desirable to use a separate conversion bath containing sodium carbonate or potassium ferrocyanide.

A specific form of material, illustrated on the accompanying drawing, may for example, comprise a support of Celluloid or similar material on which is coated a layer of gelatine containing zinc hydroxide produced in said layer in a colloidal state and as transparent as possible. Such a layer may be produced by dissolving a soluble zinc salt in a quantity of a gelatine solution and adding to another gelatine solution containing caustic soda with constant stirring after-which the mixed solution containing the zinc hydroxide precipitated in colloidal form is set, shredded and washed, and coated.

On this layer is coated a non-color sensitised, blue sensitive emulsion which is diffusely dyed yellow with a dye capable of being selectively destroyed, in the presence of and at the points occupied by a silver image, by suitable reagents to I form a dye image. On this emulsion there is cast a green sensitive emulsion followed by a red sensitive emulsion and finally there may bean antihalation layer.

Such a material is exposed through the support so that the different color sensations are recorded in the different layers of emulsion. The

processing of such a material may be effected as described in my co-pending application Serial No. 384,180 filed March 19, 1941, the firststep being development of the latent images in a developer containing a solvent for silver halide such as potassium thiocyanate, and preferably also containing sodium carbonate whereby the zinc hydroxide in the bottom layer is converted into opaque white zinc carbonate. Alternatively at a. later stage the material may be treated in a solution of sodium sulphide to convert the zinc hydroxide or other zinc salt formed therefrom during the processing into zinc sulphide. Further steps might comprise treatment in a solution containing thiourea and potassium ferrocyanide as described in said co-pending application Serial No. 378,301, and containing a proportion of sulphuric acid, which converts the undeveloped halide in the two outer layers into silver ferrocyanide and selectively destroys the yellow dye in the blue sensitive layer to form a positiveyellow image therein. Thereupon the Y the opaque white'layer a suitable support or mount white layer; and removing -ferrocyanide acidradical and to silver ferrocyanide inthe two outer layers is converted into a blue-green positive image in the outer layer and a magenta positive image in the middle layer, in a :mixed toning bath as described in said 'co-pending'application Serial No. 378,302, I

to a final support with the original, transparent support uppermost.

I claim:

layer next the support a uniform opaque white deposit of zinc ferrocyanide; applying a toning bath containing ferric and uranium salts to produce; simultaneously toned imagesof Prussian Blueand uranium ferrocyanide in two of said sensitive layers; and

finally removing silver and silver salts fromthe sensitive layers.

3. A method of producing a multi-color photographic pictureon' a photographic material in- 4 eluding a transparent support, a colloid layer coated thereon containing colloidal zinc hydroxide, and, superimposed differentially color-sensitivej silver halideemulsion layers coated thereon,

I sai'dl'method comprising exposing such material through the support;

developing latent images formed in said sensitive layers by exposure;'ap-

plying a bath containing thiourea and potassium ferrocyanide to convert the residual halide in l. A method of: producing a multi color photographic picture ona photographic material incoated thereon containinglcolloidal zinc hydroxide, and superimposed differentially,color-sensij I cluding a transparent support, a colloid layer white zinc sulphide;

tivesilverhalide emulsioniayers'coated on said colloid layer, which method comprises exposing such material throughthe support; developing the latent images formed in the sensitive emulssion layers; subjecting the material to a bath containing, thiourea and potassium 'ferrocyanide to convert the residual halide infthe layers into an image havingja ferrocyanide acid radical; toning the material in a bath containing ferric and uranium salts to produce Prussian. Blue and ura'- qjnium ferrocyanide' images in sion layers; converting two For, said emulthe colloidal zinc hydroxide in the layer nex' silver and silver salts from the sensitive layers.

2. A method of producing a multiecolor photographicpicture one. photographic material ineluding a transparentsupport, a colloid layer coated thereon containing colloidal zinc hydrox-j v ide, and superimposedv differentially; color-sepsi tivesilver halide emulsion layers. coated thereon,

the sensitive layers into a substance havingla ferrocyanide acid radical; applying a toning bath containingferric and uranium salts to produce Prussian Blue and uranium ferrocyanide'images simultaneously in two of said sensitive layers; at any stageapplying a bath of a sulphide to convert the'colloidal zinc hydroxide to an opaque and finally removing silver and silver salts from the sensitive layers.

A method of producing a multi-color photographic 'image in a'photographic material includingpa transparent support having coated thereon. a'colloidal zinc hydroxide, andcoated red "sensitive emulsion prising exposing such,

t the' support intoan opaque successively thereon-a blue sensitive silver halide emulsion layer diffusely dyed yellow with a dye capable of being selectively destroyed by the silver dye bleach. process, followed by green and layers; said method comin the sensitive emulsion layers; applying a bath containing thiourea, potassium ferrocyanide and an acid to convert the residual'halide in the two outer layers into silver ferrocyanide, and to simulataneously perform selective imagewise destruction of the dyestuff-in the blue sensitive layer; applying a toning bathcontaining ferric and uranium salts to produce a Prussian Blue image in l the outermost layer followed by a uranium ferrosaid method comprising'exposijng such material through the support; developing the latent imsaid sensitive layers; applying a ages formed in bath containing thiourea and potassium ferrothe said sensitive layers into an image having 'a produce in the cyanide, both:to convertkthe residual halide inl'j.

cyanide image infthe middle layer; at any stage converting the colloidal zinc hydroxide in the layer next the support'to an opaque white layer of a zinc salt; and removing silver and silver salts frornthe sensitive layers ALANGILBERT TULL.

v material through the support to produce component color record images

Images