US2384658A - Color photography - Google Patents

Description

agentason'eoi Patented Sept. 11, 1945 COLOR PHUIOGBAPHY rm w. Vittum, Rochester, a. 1., mi Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey I No 1mm. Application my 10, ms.

SerialNo. 494,241. I

'1 Claims. (Cl. L

' method is applicableto various types oicolor Z This invention relates to color photography and particularly to a method for preventing discoloration of photographic layers containing dye im- 'In the coupling process of color photography the dye images produced by coupling are of the indophenol, indaniline or azomethine type. Dyes produced by developing with aminophenols in the presence of a phenol or naphthol coupler are indophenol dyes and those produced by developing with a p-phenylenediamine typeflflfiloper in the presence of phenol or naphthol couplers or reacsis-as development processes such as those described in Marines, Godowsky and Wilder U. 8. Patent sesame, granted August 19, 1941,Mannes and .Godowsky U. 8. Patent 2,304,910, granted December 15, 1943, Schinzel U. 8. Patent 2,306,410,

granted December 29. 1942 and Jelley and Vittum U. 8. Patent 2,322,027, granted Junelii, i948.- These patents disclose color development proceases in which the couplers are incorporated in the developing solution, in which case-my method is applicable only to deceleration of the rinaldye tive methylene compounds are indaniline or azomethine dyes, respectively. All oi these developing agents are primary aromatic amino developing agents.

One oi. the diiilculties encountered with such images to light or conditions of high temperature or humidity. This results in more or less rapid discoloration oi the finished pictures under certain conditions of use or storage. This discoloraimage. or in the emulsion layers either as nondiiiusing compounds or incorporated in wateris the relatively low stability of the dye tion takes the form of a bleaching or less in the dye present in the layer.

In those processes where couplers are incorporated in the emulsion layers or in plain gelatin layers in the film, another difliculty frequently encoimtered is the instability to heat or light of the residual unused coupler in the layers. This unused coupler sometimes has a tendency to darken under the influence of heat and light which results in the building up oi discolored areas which are evident as lain in the highlights of the tinished pictures. 4 It is, therefore, an object of the present invention to provide a method for reventing discoloration oi photographic dye images produced by coupling. A further object is to provide a method for preventing the darkening or discoloration of residual couplers in photographic layers. Other objects will appear from the iollowing description oi my invention.

These objects are accomplished by introducing into the layers containing the couplers or dye images, or anti-oxidant or reducing agent as one oi the final stages of processing the exposedphotographic element.

immiscible solvent droplets,- in which case mymethod is useful for preventing discoloration of both the residual coupler and the dye image.

In all oi these color development processes, itis customary to remove the developed silver and any residual silver halide as a final step in the process a by treating the him with a solution oi potassium ierricyanide and potassium bromide iollowed by a hypo bath. Such treatment is described, for example, on page 2, column '2 oi the Mannes.

Godorwsky and Wilder U. 8. Patent 2,252,118, re

ierred. to above. According to my invention the film is treated aiter removal of the silver images. with an aqueous or alcoholic aqueous tsolution'oi I have found that both the decoiorization of the dye images and the darkening or discoloration of the residual couplers in photographic layers are oxidation processes involving atmospheric oxygen and may be eiiectively inhibited in many cases by the introduction into layerscontaining the dyes or couplers, of an anti-oxidant or-reducing mo O theiinalstagesotprocessing. my I6 -9 p-Bemylaminoan anti-oxidant to eii'ect an increase in the sta-' bility of the dye images or residual couplerajor both.

The following compounds have been found suit able for use according to my invention:

v on on OH 000E101! nc-o I cow cumin; 1

mm y] carbine! Ascorbic acid and isoascorbic acid phenol Eydroqumons v'loluhydroquinone Chlomhydroquinono on ononcinoa rumours-1m iii-551m Ascorbic acid can be used in any of its isomeric forms, such as d-ascorbic acid and l-ascorbic acid.

The following solutions are suitable for use according to my invention:

The anti-oxidant suggested above are preferably used in amounts of from 1 gram to 10 grams per liter 01' solution although more or less than these amounts may be employed.

Some oi the anti-oxidants suggested above, such as hydroquinone, have been used for other purposes in treating developed color-images, for example, for removing stain. For these purposes the anti-oxidant has been applied before or during development. It is essential for the present purpose-that the anti-oxidant is introduced at the end of the process or at least after the application of the oxidizing silver removal bath.

It will be understood that the examples in eluded herein are illustrative only and that my invention is to b taken as limited only by the scope or the appended claims.

' I claim:

1. The method oi'preventing the discoloration of photographic layers containing dye images selected from the class consisting of indophenol, indamine. and azomethine dyes, which comprises forming said dye'image in said layer by development of an exposed silver halide with a primary aromatic amino developing agent in the presence of a coupler compound, removing the silver images thus formed, together with the residual silver halide, and thereafter treating said layer with a solution of an organic reducing agent containing at least two groups selected from the class consisting of hydroxyl, amino, and substituted amino groups.

2. The method or preventing the discoloration of photographic layerscontaining dye images selected iron the class consisting of indophenol, indamine, and azomethine dyes, which comprises I forming said dye image in said layer by development of an exposed silver halid with a primary aromatic amino developing agent in the" presence of a coupler compound, removing the silver silver halide, and thereafter treating said layer with a solution of an aromatic hydroxy reducing agent containing at least two hydroxyl groups.

3. The method of preventing the discoloration of photographic layers containing dye images selected from the class consisting of indophenol, indamine, and azomethine dyes, which comprises forming said dye image in said layer by development of an exposed silverhalide with a primary aromatic amino developing agent in the presence of a coupler compound, removing the silver images thus formed, and treating said layer with a solution of a hvdroquinone.

4. The method of preventing the discoloration of photographic layers containing dye images selected from the class consisting of indophenol, indamine, and azomethine dyes, which comprises forming said dye image in said layer by development of an exposed silver halide with a primary aromatic amino developing agent in the presence of a coupler compound, removing the silver images thus formed, and treating said layer with a solution or hydroquinone.

5. The method of preventing the discoloration of photographic layers containing dy images selected from the class consisting of indophenol, indamine, and azomethine dyes, which comprises forming said dye image in said layer by development of an exposed silver halide with a primary aromatic amino developing agent in the presence of a coupler compound, removing the silver images thus formed, and treating said layer with a solution of an aromatic derivative of hydrazine.

6. The method of preventing the discoloration of photographic layers containing dye images selected from the class consisting of indophenol,

I images thus-termed, together with the residual ment of an exposed silver halide with a primary aromatic amino developing agent in the presence of a coupler compound, removing the silver images thus formed, and treating said layer with a solution of l-phenylsemicarbazide.

PAUL W. VII'I'UM.