US3527603A - Process for the production of color photographic images by the silver-dye-bleach process - Google Patents

Description

United States Patent 3,527,603 PROCESS FOR THE PRODUCTION OF COLOR PHOTOGRAPHIC IMAGES BY THE SILVER- DYE-BLEACH PROCESS Bernhard Seidel, Cologne-Mulheim, Jakob Kemmer, Co-

logne-Klettenberg, and Erich Bockly and Eberhard Gunther, Leverkusen, Germany, assignors to Agfa- Gevaert Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Mar. 24, 1967, Ser. No. 625,609 Int. Cl. G03c 7/02, 7/52 US. CI. 96-20 1 Claim ABSTRACT OF THE DISCLOSURE Sensitivity of silver-dye-bleach layers are increased if the bleaching step is carried out with a bleach bath that is flushed with inert gas like nitrogen, or the layer just before it enters the bleach bath is rinsed in a similarly flushed rinse bath.

. sion is, of course, greatly reduced. Due to the reduction in sensitivity azo dyes containing photographic materials for the silver-dye-bleach process are not only useless for taking photographs but are generally inferior to photographic copying materials of the conventional composition containing color couplers.

The insuflicient sensitivity constitutes one of the major disadvantages of this process.

In order to overcome this disadvantage, it has already been proposed that up to the moment of exposure to light, only colorless precursors which subsequently produce azo dyes should be incorporated in the layers, and after exposure and black-white development, these are reacted with suitable diazonium salts to form the desired image dyes which are subsequently bleached.

This process is, however, of no practical significance since there is no known diazonium salt which will at one and the same time yield suitable yellow, magenta and cyan dyes with three given coupling components. Further more, diazonium salt solutions capable of coupling are too unstable for storage. It is among the objects of the present invention to modify the silver-dye-bleach process in order to obtain a higher sensitivity of the azo-dye containing photographic material.

We now have found that the sensitivity of silver-dyebleach materials can be increased by flushing the dyebleach bath with an inert gas, preferably nitrogen, during the dye-bleach process or by using a bath saturated with an inert gas. By using this process improvements in the sensitivity, usually amounting to 0.1 to 0.9 unit log. I -t (where 0.3 unit log I -t correspond to an increase in sensitivity of one aperture stop) and considerable improvements in the fogging values, have been achieved.

In addition, a substantial improvement in the uniformity and reproducibility of processing is achieved. The process according to the invention may, for example, be performed as follows:

Before processing, the dye-bleach bath is saturated with an inert gas, preferably nitrogen. Alternatively the dyebleach bath is saturated with the inert gas and a current of inert gas is also maintained during processing. The inert gas may be introduced either in a continuous stream or intermittently. One may also wash or saturate the rinse baths immediately before the dye-bleach bath with inert gas in order to remove air from the photographic material to be bleached.

The process according to the invention is thus characterized by the fact that dyebleaching is accomplished in a bath which has been substantially or completely freed from dissolved oxygen by being saturated with inert gas. This means that, in practice, there is increased utilization of the image silver for the dye-bleach process, which results in an increase in sensitivity of the color photographic material processed in the dye-bleach process.

It has been found that the use of the inert gas is only effective in the dye-bleach bath and the baths immediately preceding it. Dye-bleaching may be performed either with a single bath or a sequence of two or more baths (in cases in which the dye-bleach process is accomplished in two or more steps). The inert gas treatment completely lacks the above eflect when carried out in the black-white developer.

The process according to the invention is thus basically dilferent from treating the color developer with nitrogen in color-forming development, where the essential effect of the nitrogen treatment is the mechanical motion in the developer caused by the ascending gas bubbles and the prevention of atmospheric oxidation of the developer substance. In the latter case, the efiect of the inert gas is greatly assisted by reducing agents such as hydroxylamine or alkali metal sulfite added to the color-forming developer. Freshly prepared color developers which have the analytical concentration of developer substance accordingly exert their full effect, and the flushing or saturation with inert gas merely serves to maintain this state as long as possible.

The process according to the invention, on the other hand, provides a bath which is distinctly superior to a freshly prepared bath. The efiect of the process according to the invention was all the more unexpected since most bleaching baths used in practice, especially those based on thiourea or on quinoline-iodide already contain reducing agents. Moreover, the effect of the process according to the invention cannot be achieved by adding other reducing agents.

The eifect of the saturation with inert gas can be eliminated by flushing with air or oxygen and can be restored by renewal of introduction of nitrogen.

The process according to the invention also has the advantage that, owing to the better utilization of dye and silver, it is possible to use image layers with correspondingly lower silver halide content. The inventive process in addition makes it possible to work with a dye-bleach bath which is not as strongly acid as usual.

Bleaching in the presence of inert gas may also be applied for reducing the quantity, e.g., of a bleaching catalyst, so that discoloration of the layer by the action of the catalyst is avoided.

The process according to the invention is, of course, not limited to the bleaching of a silver image after blackwhite negative development, but can equally well be applied to the bleaching of positive silver images such as those produced in reverse development or in direct positive processes, e.g., by the bromine ion diffusion process, the silver salt diffusion process or photosolubilization.

3 EXAMPLE 1 The following layers are applied to a baryted paper support:

1) A silver bromide gelatin emulsion which contains, per kilogram, g. of a cyan dye of the following formula:

SOaH 503B the preparation of which has been described in German Auslegeschrift No. 1,041,355, and mg. of a sensitizer disclosed in German Auslegeschrift No. 1,213,240, Example 11. The amount of silver in the finished layer is about 0.5 g. Ag./m.

(2) Intermediate gelatin layer, if desired with additives for inhibiting dilfusion.

(3) Silver bromide gelatin emulsion layer containing, per kilogram, 5 g. of a magenta dye of the following formula:

one-@sm-rrn on the preparation of which is described in German Auslegeschrift No. 1,039,840, and 15 mg. of a sensitizer for the green region of the spectrum disclosed in German Auslegeschrift No. 1,213,240, Example 2. The amount of silver applied in the finished layer is 0.5 g. of Ag/m. in the form of silver halide. The dye is rendered fast to diffusion by the addition of 1.5 g. of 4,4'-diphenyl-dibiguanide; (4) Intermediate gelatin layer, thickness 1.0-1.2m (5) Yellow filter layer having an optical density of 0.5 at a layer thickness of 1 mm.;

(6) Intermediate gelatin layer, thickness 1.0-1.2/,u (7) A slightly less sensitive silver bromide gelatin emulsion containing, per kilogram, 8 g. of the yellow dye of the following formula:

described in German Patent No. 935,565, Example 1, which layer has been rendered fast to diffusion by the addition of 3 g. of 4,4-diphenyldibiguanide. The amount of silver in this layer is about 0.55 g. of Ag/m. in the form of silver bromide;

(8) Protective gelatin layer, thickness 1.2/,u.

The above multi-layered material is exposed in a conventional sensitometer behind a grey test wedge and processed as follows:

(6) Rinsing in water for 5 min.

(7) Dye-bleaching for 25 min. in a bath of- Quinoline-SO ml.

Sodium hypophosphite-5 g.

Potassium iodide10 g.

Sulfuric acid conc25 ml. 2,3-dimethylquinoxaline0.1 g. Waterup to 1000 ml.

Rinsing in water for 5 min.

Bleach-fixing for 10 min. in a bath of- Anhydrous soda-24 g.

Sodium thiosulfate-l25 g.

Tetrasodium ethylene diamine tetraacetate-26 g. Ferric chloride-15 g.

Anhydrous sodium sulfitel3 g. Waterup to 1000 ml.

The sensitometric tests give the following results:

Uniform fog Cyan 0.34 Magenta 0.2

Yellow 0.22

(a) If a sample of the same material is processed in the same way but with additional saturation of the dyebleaching bath, by first passing a vigorous stream of nitrogen through that bath for 60 minutes before it is used,

the following values are obtained after drying:

Cyan Magenta Yellow Uniform fog 0.25 0. l5 0. 19

(=Difierence from above expcrlment) 0. O9 -0. 05 0. 03 Improvement in sensitivity over original sample (log I -t) +0. 25 +0. 35 +0. 54

Cyan Magenta Yellow Uniform fog 0. 15 0. 11 0. 17

(Difference from comparison test) -0. 19 0. 09 0. 06 Sensitivity compared with original sample (log I -t) +0. 30 +0. 55 +0.60

(0) For comparison, the dye-bleach bath is saturated with oxygen before the bleaching process 'but no further gas is introduced during the bleaching process. With this method, only incomplete bleaching is achieved and the following fog values are obtained after drying.

Uniform fog Cyan 1.95 Magenta 1.35

Yellow 0.85

The loss in sensitivity is not compensated by increasing the exposure time. Thus exposure prolonged by the factor 20 results in the following values- Cyan 1.75 Magenta 1.0 Yellow 0.55

lowing values:

Cyan 0.05 Magenta -0.11 Yellow 0.05

1 Sensitivity compared with original sample (log I -t).

(e) If a bath saturated with air according to d) is subsequently treated with nitrogen as indicated under a), the following values are obtained after drying of the sample:

Cyan Magenta Yellow Uniform fog 0. 23 0. 14 0. 17

(=Dit1erence from original sample)... -0. 11 0. 06 0. Sensitivity compared with original sample (log I -t) +0. 25 +0.35 +0. 6

Practically the same values are thus obtained as with saturation of the bath without prior treatment with air. Similar figures are obtained if the nitrogen treatment follows a preceding saturation with oxygen.

EXAMPLE 2 A photographic multilayer material is prepared as described in Example 1, except that the amount of silver in the individual layers is only 65% of the values indicated in Example 1. Such a material is bleached in the course of processing as described in Example 1, to give the following fog values:

Uniform fog C-yan 0.50 Magenta 0.50 Yellow 0.50

A sample which had been processed under the same conditions but in which the dye-bleach bath has been saturated with nitrogen and had nitrogen passed through it at the rate of 600 ml. of nitrogen per minute during the dye-bleach process gave, by contrast, the following values:

Cyan Magenta Yellow Uniform fog 0. 19 0. 19 0.21 (Difference from the comparison sample without nitrogen) -0. 31 -0. 31 -0. 29 Sensitivity compared with comparison sample without nitrogen (log I t) +0. 25 +0.10 +0.23

Similar results are obtained when instead of the dye bleaching baths mentioned in Example 1, a bleaching bath containing thiourea is used, e.g., a bath such as described in German Patent No. 1,091,429, Example 5 G.

EXAMPLE 3 The following layers are applied to a support of white pigmented cellulose acetate or a support of polyethylene coated paper which has been rendered hydrophilic:

(1) A red sensitized silver halide gelatin emulsion layer which contains, per 500 g. of a silver bromide-iodide gelatin emulsion having 6 mol percent of silver iodide, 2.7 g. of the following cyan dye:

dissolved in 250 ml. of a 2% gelatin solution to which 2.3 ml. of a 30% formaldehyde solution, 0.4 g. of saponine and as plas'ticizer are also added. The amount of silver in the finished layer is about 0.8 g. Ag/m. in the form of silver halide.

(2) An intermediate layer of 2% gelatin solution.

(3) A layer consisting of 500 ml. of green-sensitive silver bromide gelatin emulsion containing 6 mol percent of silver iodide, to which emulsion are added 2.8 g. of the magenta dye of the following formula:

IFII:

dissolved in 200 ml. of a 2% gelatin solution and 0.4 g. of saponine, 2.3 ml. of a 30% formaldehyde solution and as plasticizer. The amount of silver in the finished layer is about 0.75 g. Ag/m. in the form of silver halide.

(4) An intermediate layer of a 4% gelatin solution to which are added 8 g. of tartrazine per liter.

(5) A layer in which 400 ml. of a 4% gelatin solution containing 0.7 g. of saponine and 4.2 g. of the yellow dye of the following formula:

Cyan Magenta Yellow Uniform fog:

Without N 0. 08 0. l2 0. 17 With N 0.09 0.12 0. 17 Sensitivity increase in the experiment with N flushing (in units log 1-t). +0. 13 +0. 18 +0.37

We claim:

1. In the silver-dye-bleach process of producing color photographic images by the steps of exposing a lightsensitive photographic element comprising at least one supported silver halide emulsion layer containing on a20- dye, developing the exposed layer to form a silver image therein, and dye-bleaching the azo dye in accordance with the silver image to form a dye image, the improvement according to which the dye-bleach bath is flushed before or during the dye-bleach process, with nitrogen gas.

References Cited UNITED STATES PATENTS 2,837,988 7/1958 Pavelle -89 OTHER REFERENCES Photo Methods for Industry: Gas Burst Agitation, November 1963; pp. 5052 and 54.

Commander F. W. George, M.C., U.S.N.: A Practical System for Telecobalt Radiography, Radiology, The Radiological Society of America, vol. 80, JanuaryJune, 1963, pp. 288-289.

NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R. 96-53