US2268630A - Color photography - Google Patents

Description

Patented Jan. 6, 1942 UNITED STATE Gustav Wilmanns, Wolfen, Kreis Bitterfeld,'and

Wilhelm Schneider, Dessau, Ge

rmany, assignors. by memo assignments, to General Aniline a Film Corporation, New York, N. Y., poration Delaware No Drawing. Application January c, 1938, Serial No. 183,588. In Germany January 21, 1937 1 3 Claims.

Our present invention relates to color photography and more particularly to a process of colorforming development.

Inthe production-o1 multi-color pictures the exposed layers have heretofore been developed directly or by reversal development to produce a positive or negative silver image which, after fixing, has been converted into a silver salt and l the colored image has then been formed b a color forming developer. In this methodlay which do not contain dyestufl components may be used and the latter have been introduced into the developer for producing the colored image. For developing the various color images in their several layers a large number of treating and developing operations is necessary. so that the method is very tedious. v

'It is therefore one of the objects of this invention to provide a comparatively simple color developing process which,however, enables the operator to make necessary corrections in the color' shades and to eliminate undesirable color strains.

Further objects of this inventionwill become apparent from the'detailed description following hereinafter.

The invention is concerned with a process in which there is used a'multi-layer photographic material containing in the several layers, the suitable dyestuflf components for thcomponent pictures and the correct coloring is controlled first by simple or reversal development in the several layers to produce component silver imagesandthen, after fixing and converting the silver into a silver salt, further developing with the color forming developers. As compared with the direct development of the color image in which causes a corresponding change in color tints during the subsequent color forming development.

The developing solutions to be used may either contain different substances suitable for color I forming development or the speed of action of one and the same .or even diflerent developers may be varied by additions.

Moreover, it is possible .to correct tint oi! the image by treatment with acolor developer which-at the same time contains a dyestuii component which produces a color which 'is partly lacking or insufiicient in the finished color picture. Since in this case the action of the color forming developer is not limited to any particular layer, the method lends itself only to a comparatively small compensation of the color tint.

As dyestuff formers for the silver halide emulsion layers there may be used with advantage dyestufi components which are fast to diflusion with respect to the binding agent of the emulsion owing to the presence of certain radicals in their molecule. As described in U. S. Patent 2,179,238, groups may be introduced into the color components which impart to the molecule of the color .lormer a substantive character. As 'described in U. 8. Patent 2,178,612 the dyestufi components may be made fast to diffusion by introducing into their molecule radicals of highly.

polymeric carboxylic acids or their derivatives.

Moreover, dyestufl components become fast to difiusion when as described in U. 8. Patent 2,186,849, there is introduced thereinto an allwhich the number of necessary process steps is smaller this new method has the great advantage oi permitting control of the color tints in full daylight. Thus faulty reproduction may without difilculty be avoided and matters of personal preference in the color reproduction may be taken into consideration. For example, in printing a complementary color negative onto a multilayer positive material containing component's an undesirable color strain in the positive may be completely removed by treating this bleached-out positive in succession with difierent color formphatic carbon-chain of more than 5 carbon atoms, or, as described in U. S. Patent 2,179,244 polypeptide radicals, or, as described in U. 8. Patent 2,186,732 a carbohydrate radical, or, as

' described in U. S.' Patent 2,186,733 the radical of a natural resin, or, as described in U. S.'Patent 2,186,851 a sterol radical. Furthermore, dyestufi componentsfast to diffusion are also ""obtalned when, asdescrlbed in U. 8. Patent 2,186,- 784 the molecules of the dyestuff components are linked together to yield a chain-like molecule. It is also possible to produce dyestufl components fast to diffusion in manner described in U. 8.

Patent 2,179,228, in which the dyestufl picture is produced by azo-coupling. Generally such dyestud components are fast to diffusion which are substituted by radicals of comparatively high molecular weight (2,179,239).

As developing agents there'may-be used for example the substances described in U. 3. Patents Nos. 1,102,028; 2,146,040: 2,163,781; 2,124,612;

2,108,243; 2,122,599; 2,163,826 and 2,163,166.

The following examples illustratethe inven- .tion:'

Example 1.A multi-layer film, in which the first silver halide emulsion is pan-chromatically the color sensitized and comprises a color component which yields on color forming development a blue image, and the second layer is sensitized for green and comprises a dyestufl component which yields a red image on color forming development and the third layer is not sensitized and comprises a dyestufi. component which on color forming development yields a yellow image, is ex-' posed and thereafter developed in normal man.-

. bleached by a Farmer's Reducer whereby the pure three-color image remains. As compared with a development in which the first developer yields the dyestufl, the present method has the advantage that any desired usual black-andwhite developer may be used as the first developer and in this manner an essentially higher sensitivity attained, since it is known that a color forming developer is less powerful in its developing effect than are the usual black-andwhite developers.

Example 2.If a film treated, for example, in a manner analogous to that described in Example 1 shows an undesirable color strain produced may be by insufficiency of one of the component colors, then the defect in the film may be eliminated by a subsequent treatment. The silver produced simultaneously with the dyestufl formation is bleached out and a color developer which contains a dyestufi! component for the particular color shade lacking in the picture, is employed. For example,'if the film, owing to the lack of red, appears too greenish, a developer will be used which in addition to the color forming agent, contains a red dyestufif component, for instance grams per liter of l-phenyl-3-methylfi-pyrazolone. If, owing to the lack of blue, the film has a yellow to reddish-appearance, then there is added to the developer instead of a pyrazolone the corresponding quantity of naphthol. m y 5 Example 3'.In cases where it can be foreseen that the finished color film will show an undesirable color shade owing to the predominance reason will have a reddish strain, then there may be used as a developer's solution of 8 grams per liter of 6-methyl-amino-3-toluldine made alkaline with sodium carbonate. By this developer the tint of the color film produced will be shifted towards the green in comparison with a film developed with para-amino-dimethylaniline.

We claim: I

1. A process of producing photographic color pictures on multi-iayer photographic material comprising a plurality of silver halide emulsion layers containing dyestufi! components fast to diflusion, said dyestuff components being capable of forming a dye in the places of thesilver picture upon being contacted with -a color forming developer, which process comprisesexposing said material to light, developing the latent image thus formed with a black-andwhite developer, fixing thedeveloped picture, reconverting the formed silver into -a silver salt capable of being developed by a color-forming developer which would normally yield dyestui! images having undesired color strains, redeveloping s'aid silver salt by means of a color forming developer while compensating for such undesired color strains by using a developer having the property of shifting the color values to correct said color strains.

2. A process of producing photographic color pictures on multi-layer photographic material 7 comprising a plurality of silver halide emulsion layers containing dyestufl components fast to diffusion, said dyestui! components being sired depression of the unduly predominant colon.

of a certain colored light during exposure, this that the finished film will show a violet strain,

then this strain may be removed or profoundly modified by adding to the color developer 10 grams of aceto-acetic acid anilide per liter.

Example 4.-,-If it is known beforehand that the finished colored film for one reason or another will show acertain color strain, then it is possible to counteract this color strain by using as a developer a substance which in itself shifts the tint of the picture in a sense complementary to the undesired color strain which is If, for example, it is known that the film for some capable of forming a dye in the places of the silver picture upon being contacted with a color forming developer, which process comprisesexposing said material to light, developing the latent image thus formed witha black-and-white developer, fixing the developed picture, reconverting the formed silver 'into a silver salt capable of being developed, redeveloping said silver salt by means of a color forming developer containing a dyestuif component, capable of forming a dye with the oxidation product of the developer complementary to the color previously determined to unduly predominate in the final picture, in an amount sufllcient to eifect the de- 3. A process of producing photographic color pictures on a photographic material comprising.

three superposed silver halide emulsion layers containing dyestuff components fast to diffusion, said dyestuif components being capable of forming a dye in the places of the silver picture upon being contacted with a color-forming developer, which process comprises exposing said material to light, developing the latent image thus formed with a black and white developer, fixing the developed picture, reconverting the formed silver into a silver salt capableof being developed, redeveloping said silver salt by means of a colorforming developer, bleaching the silver formed by development, determining any undue predominance of one of the three subtractive colors in the three color picture thus produced, and developing again with a color-forming developer containing a dyestufi' component capable of forming a dye with the oxidation product of-said color-forming developer complementary to the color unduly predominant in said picture.

I .QUSTAV WILMANNS.