US1968956A - Colored photographic image and method of producing same - Google Patents

Description

Aug. 7', 1934.

H. D. MURRAY El AL 1,968,956 COLORED PHOTOGRAPHIC IMAGE AND METHOD OF PRODUCING SAME Filed May 9 1931 Patented Aug. 7, 1934 up COLORED PHOTOGRAPHIC macs ABID METHOD OF PRODUCING SAIHE Humphrey Desmond Murray and Douglas Arthur Spencer, South' Kensington, London, England, assignors of one-third to Colour Photographs (British and Foreign) Limited, London, England, a company ofEngland 1 Application May 9, 1931, Serial No. 536,306

In Great Britain June 20, 1930 16 Claims. (01. 95-88) The present invention is for improvements in colored photographic images and the manufacture of same and concerns the manufacture of colored images in azo-dyestufis. The invention is adaptable to the twoor three-color process of color-photograph production, and is particularly applicable to the manufacture of colored films utilizable for cinematographic purposes.

The process of the invention consists essentially in this, that a diazo-compound is combined or mordanted with a metal salt image, for example, a silver-salt image, which may be produced according to the known methods of the photographic art, and the diazo-complex is then coupled with an azo-dyestufi coupling-component of the type requisite to give the color desired. By repeating the process with another image-support, for example, a film, or upon the other side of the same support, with appropriate variation in the .dyestufl components, two superimposable, or two superimposed, colored images may be obtained; and by similarly treating a third support, three differently colored superimposable images may be produced.

The invention will hereinafter be described in its application to the conversion of silver-salt images, which may be obtained by any of the known processes of photography, into azo-dyes. It is to be understood, however, that the invention is not limited to treatment of an image composed of a salt of silver but is broadly applicable in this respect to the treatment of an image composed of a salt of any equivalent metal to silver, that is to say a metal which is capable of being converted into a water insoluble salt by bleaching when coated in a gelatine or other colloid layer.

We have found in our researches that when anoriginal silverimage isconverted by any of the processes of photography known as bleaching into an insoluble silver salt or an insoluble complex-possibly a double salt-of silver and another metal, such insoluble silver derivative may be caused to combine with a diazo-compound, and the diazo-group in the resulting product can, in its turn, be coupled with an azo-dyestuif. coupling-component to yield a dye.

The invention, therefore, comprises as a new article of manufacture a support, for example, a

mm, carrying upon one or both .of the surfaces a photographically produced metal salt image in union with a diam-complex in a, condition to couple with an azo-dye coupling-component to give an azo-dye.

Advantageously, the coupling-bath for production of the azo-dy'e comprises a substance capable of rendering thesilver salt present in the silverdiazo-complex soluble in water. Such substances are known in photography as fixing agents. We

have found as a general rule that, in the absence of these fixing agents, an image constituted. by a silver-salt-diazo-complex tends to be only partially converted into an azo-dye when treated in the coupling-bath, even when the latter is brought to the correct degree of alkalinity for rapid coupling. This phenomenon calls for more particular regard, when depth of color, especially by transmitted light, in a given image or number of images, is a desideratum. The amount of azodye produced varied according to the nature of the coupling-component. Thus, some of the amino-naphthol-sulphonic acids in the absence of silver-salt solvents are capable of producing an image which is superficially colored when viewed by reflected light, but displays little depth of color when viewed by transmitted light after removal of the residual silver-salt in the image. On the other hand, coupling-components such as the naphthol-carboxy-acid-anilides appear to be incapable of coupling with these silver-salt-diazocomplexes in the absence of a solvent for the silver-salt constituent of the complex. A possible explanation is that the former classof coupling components, being themselves capable of combining with the said silver-salt constituent,

dissolve the superficial layers of the image and liberate suflicient diazo-compound to couple with the excess of azo-coupling component in the coupling solution. In any event, a simple preliminary experiment suffices to determine the behaviour of a given coupling-component, but our experience goes to show that, where depth of color is sought, the inclusion of a fixing agent in the coupling-bath is to be generally recommended. Soluble thiosulphates, cyanides and sulphocyanides are suitable fixing agents, but the 7 metal or equivalent radical of the salt should not be one capable of forming an insoluble derivative with the diazo-compound, thus interfering with the normal course of the coupling-reaction. A1- kali salts, such as those of sodium and potassium, are convenient and utilizable, but the ammonium salts are not to be recommended as they'tend to decompose in the alkaline coupling solution with loss of ammonia. Thiosulphates are preferable to sulphocyanides as the latter display a tendency to soften the gelatine of the emulsion.

The bleaching of the original silver image ma may be employed. The bleaching agents may be any of those known in the photographic art, with the proviso that, when a composite bath is used, the agent'employed must neither decompose nor precipitate the diazo-compound. Examples of suitable composite baths are given hereafter. We have found it to be generally more convenient to employ a separate bleaching bath, and that preferred is a 5 per cent. aqueous solution of cupric oride, which acts quickly, is stable, and is fi dily washed out from gelatine emulsions.

After bleaching, the image should be washed in distilled water or in water very slightly acidified with acetic acid. This precaution need not be taken when the washing water is free from salts, such as dissolved carbonates, liable to cause precipitation of insoluble compounds of the copper or other metal in-the bleaching agent within the emulsion of the silver print. Such insoluble metallic salts are capable of mordanting diazonium compounds, and produce fog" in the finished picture.

For practical reasons, it is advisable to work with those diazo-compounds which are reasonably stable in aqueous solutions at normal temperature. Diazonium salts prepared from the following amines fulfil this requirement as well as providing for a wide range of colors:-

p-amino-dimethyl-p-phenylenediamine. p-amino-diphenylamine. pp-diamino-diphenylamine. p-amino-triphenylamine. p-amino-diphenylurea.

To increase the stability of the solution of the diazo-compound for the treatment of the silversalt image, said solution may comprise an acid substance, for example, an organic acid such as citric acid.

In our experience, it is very advantageous also to include in the solution of the diazo-compound an agent to depress the hydrogen-ion concentra- I tion of the solution. Such an agent is provided by the neutral alkali salts of weak acids, for example, organic acids such as citric acid.

The azo-dyestuff coupling-component may be an amine or a phenol, a phenol-sulphonic acid, or an amino-phenol-sulphonic acid.

When coupling is effected in an alkaline solution containing a non-volatile alkali, such alkali may be provided by an alkali hydroxide or by a salt, such as sodium borate, which becomes alkaline by hydrolysis.

The coupling reaction is improvedin general, accelerated-by the presence in the coupling-solution of sodium or potassium citrate in adequate quantity. which we have found is generally above 10 per cent. Such use of a citrate is usually desirable but is not essential.

The coupling (developing) solution may advantageously also comprise an agent to increase the insolubility of the synthesized dyestuif. Such agent may be one of those commonly used in the dyestuif-industry for salting-out dyestuifs from solutions, for example, sodium chloride, sodium sulphate and sodium phosphate. 7

The following are examples of ways in which the invention may be carried into efiect, and it will be appreciated that these examples are given by way of illustration of the invention and not in limitation thereof.

Example I An untoned silver print, on glass, paper, celluloid or other support, is soaked in water and immersed in the following composite bath until the image has been converted from black to an orange color:--

A. Cuprie sulphate 30.0 gms.

Potassium citrate 200.0 gms. Potassium ferricyanide 20.0 gms. Water 1000.0 0. c.

B. p-diazo-diphenylamin sulphate 3.5. gms. Water 1000.0 0. 0.

Solutions A and B are mixed just before use. The treated print is washed, and the dye-image In place of the copper sulphate in the bleaching bath of Example I, 20.0 gms. of chromium sulphate may be substituted; or the following bath may be substituted for the component baths A and B:,-- 2" Potassium ferricyanide 13.0 gms. .Lead nitrate 7.0 gms. 10 per cent. acetic acid 100.0 0. c. p-diazo-diphenylamine sulphate---" 3.0 gms. Water 900.0 0. c.

An untoned silver print is bleached in a solution of copper chloride or in a solution of potassium bichromate acidified with hydrochloric acid.

After washing, the bleached print is immersed in the following. solution:-

The print is rinsed, washed in a solution of 2 per cent. potassium iodide until the background is clear, and development then effected by treatment with the following solution:--

Phloroglucinol 5.0 gms. Sodium biborate 50.0 gms. Sodium thiosulphate 250.0 gms. Sodium sulphate 200.0 gms.

Water; 1000.0 0. c. The developed print is thoroughly washed and then dried.

The following is an example of one way of producing a picture in three colors according to the invention:--

Example IV is to say, a developer which doesfr'not harden or color the gelatine so as to interfere with full development of the color of the azo-dye within the emulsion. The developed prints are bleached in a bath of 5 per cent. cupric chloride solution omitted 11 the sodium salt of the "H-acid" be used.

(3) For the yellow printing image:- water 150 c. c. Potassium hydroxide 3.25 gms. Sodium thiosulphate 60.0 gins. Potassium citrate 30.0 gins.

thiosulphatein the above until no further change is observed. This takes about 1-2 minutes. The bleached prints are washed for 10 minutes in distilled water, and then immersed in a bath made'up as follows:-

A. Water 100 c. 0.

Potassium citrate 20- gms. Citric acid 5 gms.

Potassium iodide 2 gms.

B. p-diazo-diprenyl'amine sulphate 1.0 gm.

Water 100.0 0. c.

25 c. c. of Solution 13 aremixed with 100 c. c. of Solution A and the print treated with the mixture.

The purpose of the presence of the citric acid is, as already stated, to stabilize the diazonium salt. The mixed solution keeps two or three days. but in the absence of the acid begins to decompose within about an hour of mixing the two solutions. 1

The prints are kept in the above sensitizing bath for -10 minutes. A longer immersion has no appreciable effect. They are thenwashed in running water for 1 minute and subsequently in a 2 per cent. solution of potassium iodide until the background is perfectly clear. This prevents. decomposition of the silver-diazo-complex and loss of the diam-compound from the image, but does not aifect the rate of washing out from the background. This washing takes 5-10 minutes, and may be continued up to minutes without visibly 'a'ifecting' he color of the final image in any way. Several hours washing appreciably reduces the final color only in the high lights. The washed prints are respectively developed in the following baths:-

(1) For the red printing image:- Water 100 c. c. Borax 5 gms. Sodium thiosulphate- 40 gms. Potassium hydroxide 0.5 gm.

Potassium citrate 20gms.

lene-3-sulpho-acid) 1.0 gm.

If the sodium salt of the "J-aci "be used, the potassium hydroxide may be omitted. (2) For the-blue printing image:

As "before, the potassium hydroxide may be h The solution'is saturated with m-cresol, filtered and then diluted by addition of c. c. of water to the filtrate.

Coupling in each of these baths is complete in about three minutes. Further immersion-has no effect upon the images. 2 guns. of potassium cyanide or 5 gins. of potassium sulphocyanide may be substituted for every 30 guns. of the sodium formula. In the case of cyanide the coupling baths act rather more 'tration of sulphate ions,

phate weakly acidified quickly, but the colors produced appear to be .slightlyless transparent than those obtained when thiosulphate is used.

The prints after coupling are washed in a solution of 5 per cent. potassium alum until free from thiosulphate. This takes about l0'minutes. If

the prints be not washed, sodium thiosulphate tends to crystallize out on the surface on drying; and if they are washed in plain water the dyes produced from the J-acid" and H-acid may run to some degree. By washing in 5 per cent. potassium alum, the sodium thiosulphate is displaced and the alum drying.

The prints are finally dried,'and are then ready for superimposition for a The potassium alum prevents running in all images formed from sulphonic acid couplingcomponents. The dissociation, and hence the solubility, of these sulphonic acid dyestuffs can also be reduced by using acid wash-water and having present an excess of a strongly dissociated ion such as the chloride, ion. Potamium alum is both acid (by hydrolysis) and ionizes strongly. To produce a large concenpotassium alum may be solutionof sodium sulwith sulphuric acid, for example, one-half per cent. A strong acid solu-.

three-color effect.

replaced by an aqueous tion will soften the gelatine of the emulsion.

Sodium sulphate acidified with potassium metabi'sulphite 'may also be used as an insolubilim'ng agent. Potassium alum presents the special recommendations of being easily available and combining in one substance the two insolubilizing factors.

The invention permits of the production of two separate and distinct images toned in different colors in the same emulsion layer, one image disposed beneath the emulsion and the other upon the surface thereof, the following being, with reference to the accompanying drawing, an example of this application of the invention:

Example V A supporting base 1 thickly coated with an emulsion 2 of soft character is stained with a dye which can be removed completely from the emulsion by washing. The dye used is one which absorbs the major portion of the light of that wave length to which the emulsion is sensitive, and thus hinders the penetration of light through the emulsion. An example of a dye for use with bluesensitive emulsions is quinoline yellow (B. D. (3. color index No. 801). The .base is soaked for six minutes in a 2per cent. solution of the dye, rinsed very rapidly in distilled water, blotted with clean blottin -paper and rapidly dried, all these operations being carried out in the dark or by the light of an appropriately screened illuminant. base 1 is then clipped between two negatives 3, 4 in register of the same object exposed behind the two filters commonly used for two-color photography. The base is then exposed tov a light of suitable intensity, first on the face and then through the back. After development, fixing and washing, one image will be observed to lie on the does not crystallize out on,

sulphate or phosphate surface of the emulsion 2 and the other image at the back. Theseimages 5, 6 (see Figure 2) are now bleached in the manner described in Example IV above. They are washed in a 2 per cent. solusince the solutions penetrate thewet gelatine more quickly than when the latter is dry.

The dried print is placed in either the red or the blue toning bath of Example IV, according to whether the red-printing image or the blueprinting image is on the surface of the emulsion. The length of time of immersion is influenced by the nature of the emulsion, but for any particular emulsion may be determined by a simple trialand-errorexperiment on the correct balance of color in the finished product. The print is then immersed for three minutes in a bath of the following composition:-

Water 100 c. 0. Potassium iodide 2 gms. Potassium alum Bgms.

and is then placed in the alternative toning bath until the coupling is complete; The print is then washed and dried as before. a

If the print be too short a time in the first coupling bath, that image which lies at the surface of the emulsion will be toned an impure color; and if the print be kept too long in the said first bath, the image which lies at the base of the emulsion will be of an impure color.

The object of the bath intermediate between the two coupling baths is, firstly, to stop by the acid-reaction of the bath, theaction of the first coupling-agent, secondly, to wash out the coupling-agent; and, thirdly, to prevent the diazocompound from being washed out at the same time, this end being obtained by the presence of potassium iodide in the bath. If cyanide or sulphocyanide be substituted for the thiosulphate in the coupling baths, the potassium alum may be replaced by a weak acid, for example, acetic acid, of a concentration such that the bathcontains 1 per cent. of the acid, expressed as glacial acetic acid.

Summed up, therefore, the invention comprises the conversion of positive images of silver into corresponding images of transparent, water-insoluble colors substantially free from silver. A wide range of colors is obtainable, inter alia those suitable for twoand three-color projection, and many of the available colors are spectrographically pure. The process of conversion is a chemical one capable of being carried to completion and the conversion of the original metallic image into the corresponding coloring matter may be in constant proportionality. Thus, if a number of silver positives of equal density are treated according to the invention the resulting prints may be obtained of equal intensity of color, The process may be operated continuously and rapidly; and, by appropriately adjusting the time of the-passage through the different baths according to their constitution and the purpose in view, may be rendered practically automatic, the final effect obtained being; ceteris paribus, dependent upon the degree of definition ofthe original metallic image. This is of great importance; in any method of three-color printing. The three metallic images are balanced in printing and developing by well-known methods of density control, and are then converted, practically automatically, into color prints in which the color balance is correct. There is here a distinct contrast with existing methods of cinematographic color printing in which the lack of color balance and adequate color controlare frequently very apparent.

By the use of opposed rollers or like-acting relatively disposed spreading devices, both sides the surface thereof.

of the image support may be simultaneously or successively treated with the same or a different solution. As already stated, two separate and distinct images toned in diiferent colors may be Produced in the same emulsion layer, one disposed beneath the emulsion and the other upon Owing to the water-insoluble nature of the colors obtainable, two or more images may be applied to one side of the support either by recoating or by transfer. As the process permits of the toning of two separate and distinct images in the same emulsion layer, a three-color record on one support may be pro- I duced, with only one wetting of the support, by employing stock coated on both sides with 90 emulsion. The invention further provides for the ready realization of a wide range of colors, and the production at will of colors in insoluble azo-dves by reason of the formation of the latter in situ from soluble components.

The following articles may be produced by the invention:-

l. A base, for example, a film, having upon one or both of the surfaces the combination of a metal salt image and a diazo-compound capable of coupling with an azo-dyestuff coupling component to give a dye.

2. A diazo complex of a. bleached metallic image capable of coupling with an azo-dyestuff coupling component to give a dye, on a transparent water-insoluble base toned in color.

3. An azo-dye image on a transparent waterinsoluble base, the image having been produced by coupling a diazo-complex of a. bleached metallic image with an azo-dyestuif coupling component.

4. A similar image to 3 transferred by any of the known means from a water-insoluble base to paper.

5. Two or more images according to 3 in two 115 or more colors superimposed to give a transparency in natural colors.

6. Two or more images according to 4 in two or more colors superimposed to give a picture in natural colors.

7. Two images according to 3 on either side of the same transparent water-insoluble base toned in different colors to give a transparency in natural colors.

8. Two images according to 3 lying at different levels of an emulsion on a water-insoluble base and toned in difierent colors to give a transparency in natural colors.

9. Three images according to 3, two lying at different levels of the emulsion on one side (i a water-insoluble base, the third lying in the emulsion on the opposite side of the base, all three images being toned in different colors to give a color transparency in natural colors.

Although the result of treating the metal-salt image with the solution of the diazo-compound is referred to herein as a combination, this mode of reference is not to be taken necessarily to mean that there is a combination in the strict chemical sense. The nature of the union and 01' the product is not yet known. The fact stands, however, that when a metal-salt image is treated with a diazo-compound according to this invention, a union of some kind takes place between the two, and the resulting complex may be caused 145 to react with an azo-dye coupling component toyield a dye reproducing the original metallic image.

We claim: 4

1. The manufacture of colored images which 150 comprises bleaching a silver image, combining the bleached image with a diazo-compound, and coupling the diazo-complex with an azo-dyestuff coupling-component.

2. The manufacture of colored images which comprises combining a diazo-compound with a silver salt image and coupling the diazo-complex with an azo-dyestuff coupling-component.

3. The manufacture of colored images which comprises combining a diazo-compound with a bleached silver image and coupling the-diazocomplex with an azo-dyestuff coupling-com- 4. The manufacture of colored images whch comprises simultaneously treating a silver image with a bleaching agent and the solution of a diazo-compound, and thereafter coupling the silver-diazo-complex with an azo-dyestufi coupling-component.

5. The manufacture of colored images which comprises bleaching a silver image with a solution of cupric chloride, treating the rec-bleached image with the solution of a (Haze-compound, and coupling the silveradiazo-complex with an az0- dyestuff coupling-component.

6. The manufacture of colored-images which comprises treating a silver image with a solution comprising cupric chloride and a diazonium salt, and coupling the silver-diazo-complex with an azo-dyestuif coupling-component.

'7. The manufacture of colored images which comprises combining a diazo-compound witha bleached silver image and coupling the diazocomplex with an azo-dyestuflf' coupling-component in presence of a fixing agent,

8. The manufacture of colored images which comprises combining a bleached silver image with a diazo-compound, washing the so-combined image with a solution of a soluble iodide, and thereafter combining the diazo-complex with an azodyestufi coupling-component.

9. The manufacture of colored images which comprises treating a bleached silver image with the solution of a diazo-compound stabilized by the presence therein of an acid.

10. The manufacture of colored images which comprises treating a bleached silver image with the solution of a diazo-compound stabilized by the presence therein of an aliphatic polybasic acid.

11. The manufacture of colored images which comprises treating a bleached silver image withthe solution of a diazo-compound comprising an agent to depress the hydrogen ion concentration of the diazo-compo'und solution.

12. The manufacture of colored images which comprises treating a bleached silver image with the solution of a diazo-compound stabilized by the presence therein of an acid and comprising an agent to depress the hydrogen ion concentration of the diazo-solution.

13. The manufacture of colored images which comprises combining a bleached silver image with a diazo-compound and converting the diazocomplex into an azo-dye by treatment with a-coupling solution comprising an alkali citrate in concentration sufficient to accelerate the combination of the azo-dye coupling-component with the diazo-complexof-the image.

14. As a new article of manufacture, an image support carrying on at least one surface a bleached silver salt image in combination with an uncoupled diazo compound.

15. The manufacture of colored images which comprises bleaching a photographically produced image composed of a metal convertible into a water insoluble salt by bleaching, combining the bleached imagewith a diazo-oompound, and coupling the diazo complex with an azo-dyestufi coupling-component. a

16. The manufacture ofcolored images which comprises simultaneously treating a photographically produced image composed of a metal convertible into a water insoluble salt by bleaching, with a bleaching agent therefor and the solution of a diaz'o-compound, and then coupling the diazo-complex with an azo-dyestuff couplingcomponent. a

f HUMPHREY DESMOND MURRAY.

DOUGLAS ARTHUR SPENCER.

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