US2013159A - Process of chemically transforming photographic images - Google Patents

Description

Patented Septo 3, 1935 attain PROCESS CHEMICALLY TRANSFORMING PHOTOGRAPH-[IO WAGES Friedrich Lieu-g, Dresden, Germany No Drawing. Application April M, 1930, Serial No. 444,359. In Germany April 1-7, 1929 2 Claims.

This invention relates to a process of chemically transforming photographic images.

In order to transform the silver of photographic images into other combinations only such 5 photographic processes are known up to now in which the silver of the photographic image has been transformed, by way of the ferricyanide process or by means of oxidizing or halogenizing reagents, into other combinations by which may be produced tone images, intensifications of theoriginal silver image or dye images'in case the obtained parts possess mordanting action. However if it is desired to utilize, in place of the reduced silver image, the silver halide residual image, the possible ways of transforming the same are-small if it is not first reduced, because according to the known processes it can be transformed into silver iodide or brown silver sulphide only.

The present process, now, opens up new possibilities of obtaining chemical compounds by way of the photographic silver image, or of the silver halide residual image, in a very simple manner, the said images hitherto being incapable of being converted at all into these compounds, or

only in a very complicated manner.

The essential feature of the process according to the invention consists in subjecting the image forming substance for instance AgBr, AgCl to the action of complex forming solvents, chemical agentsbeing added to the latter which together with the complex combination result in soluble reaction product.

The process of the chemical reaction or transformation according to the present invention is mainly a physical process, that is to say a double or mutual reaction or transformation is attained by employing a dissolving process in combination with a simultaneous precipitating process. In order to properly carryi iiut such chemical reactionijor transformation according to the present process, the image formingsub'stance, for which AgBr or AgCl is preferably selected, is subjected to the action of a solvent which possesses a strong solvent action for the said substance while the solution and the agent added to the solvent, must be insoluble or only slightly soluble therein. The function of the process may be best understood by an example with a simple solvent alan inthough this permits only a limited selection of transforming possibilities.

For instance, if a silver chloride image is treated with ammonium molybdate, which is dissolved in diluted ammonium hydroxide, the silver chloride will be dissolved in the ammonium hydroxide and transformed with the ammonium molybdate into silver molybclate which is slightly soluble in diluted ammonium hydroxide and 'pre- I cipitated in place of the former silver chloride image. In connection with this transformation and all hereinafter described transformations, the solvent is used according to the present process not unnecessarily concentrated but 'in a dilution which effects a good but not too quick solution of the image substance, in the above case a solu-, tion of about 10% ammonium hydroxide. The transforming agent, for instance, ammonium molybdate is added thereto usually concentrated.

The required exact addition is due to the fact that M the precipitating process, whose speed. depends on the concentration of the precipitating agent, must take place more quickly than the dissolving process. A too high concentration of the precipitating agent is therefore not detrimental but only a concentration which is too low because in this case the precipitation does not take place, as is required, spontaneously at the place of the image but only after the solution in the bath. The proper concentration of the transforming agent must therefore be determined very quickly so that no detail of the transformation image may be lost otherwise the concentration of the transforming agent must be increased.

According to the present invention, in order to transform the silver image into other chemical products, complex combinations are advantageously employed, which either are formed in.

'the photographic image by forming double salts or which possess the feature of being contained in the silver halide, a process which will be described more specifically hereinafter.

A formation of the kind of a double salt solution and its further use forchemical transformation according to the present process takes place in the following manner by way of example: The silver halide image is bathed in a diluted solution of about 2-5%, manganic thiocyanate whereupon the silver halide becomes transparent to the extent of the formation of its complex combination. In lieu of the former transformed silver halide image, a compound is obtained whichis capable of reaction and can be used for further transformation. By means of the thiocyanate group cyanate reducing reactions may be carried out, as hereinafter described, or the manganese may be used for oxidation processes by transforming the same in the known manner by an alkaline of the. added manganic thiobath into a manganese dioxide image from which oxidation dye images can be produced.

However far more possibilities of reaction are given when using such complex combinations which have been called formation hereinbefore, because by the same it is possible to finally transform in a most simple manner the silver image into any desired chemical combination as will be described hereinafter. Compared with the above loose addition, or double salt combinations, certain organic combinations possess the property of combining with metallic salts, preferably salts of silver, mercury, copper and lead, and form with the same very characteristic new complex combinations. This property will be frequently found in the case of the carbamide or urea group and the thio-urea group. For instance guanidine H2N.C(NH) .NH2 with silver salts combine to form a new member silver guanidine HzN.C(NH) .NHAg. I

. otherwise do not produce an insoluble combination with silver, may therefore also form with the photographic silver image a water-insoluble combination, which may then be used in any desired manner for further chemical transformation.

. If, for instance, a silver image is bleached in the known manner to form a silver chloride or bromide image and the latter' is bathed in a thiosiamine solution of to 1% to which is added sodium phosphotungstate in a concentration according to the above-mentioned indications 2. silver phosphotungstate complex will be precipitated as the silver halide passes into solution in the thiosiamine. This precipitated matter is a means for fixing basic dyes in a waterproof and light fast manner. Therefore it is possible to obtain dye images by bathing the phosphotung'state image in a solution of a basic dye and subsequently removing the phosphotungstate image by treatment in a solution of thiosulphate.

If in lieu of the sodium phosphotungstate another salt is added to the thiosiamine bath, this silver salt will be .quantitatively precipitated in an insoluble form in a few seconds in lieu of the former silver halide image.. By adding potassium ferrocyanide, a silver ferrocyanide image is obtained which may be transformed in the known manner into toning images etcetera. In view of the character of these silver com plexes to yield with substances insoluble combinations, it is possible to produce photographic images also with these substances and subsequently to carry out chemical processes, 'which have not been attained heretofore with the common photographic baths. For instance or- 'ganic sulphonic acids are precipitated in the a presence of the said complex formers as comamino-3-6-disulphonic acid on a silver bromide image, a corresponding complex silver image is produced in its place. Most of the azo dyes possess as components organic sulphonic acids and therefore azo dye images of an unlimited variety can be produced by the transformation of the silver image into the same and by a subsequent coupling bath with diazo components.

The insolubility of the respective complex silver combinations depends on the choice of the respective complex formers, and therefore in many cases preferably dialkylated thio-ureas, thiosemicarbazide, guanidine or similar suited substances are used in place, of thiosinamine.

Instead of adding to the complex-former that group (for instance, N03) which is to be combined with the silver image in the form of a salt (for instance, NaNOa), in order to precipitate it at the place of the silver image in the described manner, it is possible to combine the desired "groups directly with the complex-former (for instance, guanidine nitrosylsulphuric acid) whereby it is directly embodied in the silver image without any process of dissolution.

In addition to these complex silver images also image intensifications may be directly produced by subsequently treating the bluish toned or dyed silver image in an alkaline bath. Silver sulphide is formed by the alkaline bath, which former intensifies the blue image and at the same time renders it black, if a readily decomposable sulphur compound is employed as complex-former.

Of these complex-formers especially the thiocarbamide possesses a characteristic which in a purely physical way can be used for producing photographic dye images. If in addition to the thiocarbamide a silver compound is used which is quite insoluble in the same and if concentrated thiocarbamide of about,5% is used, the image will be transformed into "a transparent caoutchouc-like substance. Thelatter closes the pores of the gelatine at the image-places in a watertight manner as if the same had been treated with resin. After the image has been dried, it is placed into an acidic dye-solvent and at the same time a silver-compound'is taken which does not show any causticity for dyes. In view thereof the dye is fully repelled at the places of the complex silver image and, by its imbibition into the remaining part of the gelatine, a negative dye image is produced compared with the initial image.

What I claim is:

1. Process for toning silver images consisting in transforming the silver into silver halide, and subjecting the transformed image to a bath containing a complex forming solvent for the silver halide of the group of thiosinamine, thiourea, thiosemicarbazide, guanidine and containing also a reagent which immediately forms an insoluble precipitate with the silver complex, but which does not react with the silver halide.

2. Process for toning silver images consisting in transforming the silver into silver halide and subjecting the transformed image to a bath containing a complex forming solvent for the silver halide of the group of thiosinamine, thiourea, thiosemicarbazide, guanidineand containing also azo dye components having a sulfonic acid grouping.

FRIEDRICH LIERG.