Simultaneous Bleach-fixing Method In Color Photography

Abstract

In processing photographic light-sensitive color material, bleaching can be promoted without the occurrence of color stains by incorporating, in a bleach-fixing solution containing a water-soluble iron complex salt or a processing solution, between color development and bleach-fixing a compound shown by the general formula ##SPC1## Where R.sub.1 and R.sub.2 are an alkyl group, an hydroxyalkyl group, an aryl group, or an allyl group, or R.sub.1 and R.sub.2 can form together a hetrocyclic ring, and R.sub.3 is an alkyl group, an hydroxyalkyl group or an allyl group when R.sub.1 and R.sub.2 do not form a heterocyclic ring and is hydrogen, an alkyl group or an hydroxyalkyl group when R.sub.1 and R.sub.2 form a heterocyclic ring.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved bleach-fixing method in photographic color processing.

Color processing, in general, consists of a number of steps, such as, color developing, stopping, bleaching, fixing, hardening and stabilizing, which need various chemicals depending on the light-sensitive materials to be processed. Such processings are carried out, for example, by passing the material to be processed through a color developing bath, a stop fixing bath, a water washing bath, a bleach-fixing bath, another water washing bath, a hardening bath, a further water washing bath and a stabilizing bath. The material may be passed through the successive baths by leader belt and and roller means.

2. Discussion of Prior Art

Two typical bleaching methods in the processing of color photography as mentioned above, are that of using potassium ferricyanide and that of using a water soluble iron complex of ethylenediaminetetraacetic acid. In the case of using the former, the bleaching power thereof is sufficient to keep the picture quality, but the bleaching bath and fixing bath must be separated, because thiosulfate suffers decomposition from mixing with potassium ferricyanide. Therefore, this procedure requires a longer processing time.

Moreover, potassium ferricyanide tends to be converted into potassium ferrocyanide. In the case of using the latter, on the other hand, the bleaching and fixing power is not always sufficient, but the coexistence of the oxidizing agent and thiosulfate is possible. Therefore the bleaching and fixing can proceed simultaneously in one bath. In this case, thiourea or its derivative, as is well known in the art, may be added to the bleach-fixing bath so as to increase the bleaching utility. When adding thiourea or its derivatives to a bleach-fixing bath, however, color stain often occurs from contamination of bleach-fixing solution with the color developing solution. This phenomenon has been proved to relate closely to the construction of photographic materials and the type of photographic emulsions. For example, the upper layer is more susceptible to color stain. Therefore, in a color printing paper consisting of a red-sensitive layer with a cyan coupler as the uppermost layer, a green-sensitive layer with a magenta coupler as the middle layer, and a blue-sensitive layer with a yellow coupler as the lowermost layer, for example, cyan color stain occurs. Conversely, in a color printing paper having a blue-sensitive layer containing a yellow coupler as the uppermost layer, a green-sensitive layer containing a magenta coupler as the middle layer, and a red-sensitive layer containing a cyan coupler as the lowermost layer, yellow color stain occurs. In a color positive film having three emulsion layers in the following order, from the top, a green-sensitive layer containing a magenta coupler, a red-sensitive layer containing a cyan coupler and a blue-sensitive layer containing a yellow coupler, a magenta color stain occurs. Such a phenomenon occurs even in the presence of an extremely small amount of thiourea or its derivative, for instance, a 10.sup..sup.-6 - 10.sup..sup.-7 g./1. color-developing solution thereof. Furthermore, it is nearly impossible to prevent such color stain, since many of the thiourea derivatives have absorptive properties and the elimination thereof is very difficult.

Such color fog formation is observed in following cases although it may also occur in many other cases.

1. When using a leader belt made of synthetic fiber, such as, nylon in a continuous processing system as described above, thiourea or its derivatives are absorbed on the leader belt and cannot be completely eliminated during the processing steps after bleach-fixing; that is, during the stages of washing, hardening, final washing and stabilizing. Therefore, thiourea or its derivatives, absorbed on the leader belt, enters into the color developing solution, resulting in color stain.

2. Even in the processing using a developing tray, there sometimes occurs the above-mentioned color stain if the color development is carried out in a tray wherein a bleach-fixing solution containing thiourea or its derivatives have been applied, or if the developer accidentally happens to be contaminated even to a slightest degree with the thiourea derivatives.

SUMMARY OF THE INVENTION

As a result of various studies or efforts to overcome this disadvantage, that even the slightest amount of contamination of thiourea or its derivatives results in color stain, it is found that a compound (I) derived from thiourea, gives no color stain even if it enters into the color developing solution, and furthermore its ability to accelerate the speed of the bleaching reaction is comparable to or better than that of thiourea. This compound (I) is represented by the general formula, ##SPC2##

wherein R.sub.1 and R.sub.2 are alkyl, hydroxyalkyl, aryl and allyl groups or they may be linked together to form a heterocyclic ring, R.sub.3 is an alkyl, hydroxyalkyl or allyl group when R.sub.1 and R.sub.2 do not form a heterocyclic ring, and hydrogen, alkyl group or hydroxyalkyl group when they form a heterocyclic ring. The compound (I) showed remarkable acceleration of bleaching reaction in every case where it is added to a bath between the color developing and bleach-fixing, or to a bleach-fixing bath itself.

Illustrative of the compound of the foregoing general formula, used in the practice of the invention, are the following, although it is not limited thereto only. ##SPC3##

Compound 1 may be synthesized in the conventional manner by heating ethylenediamine with carbon disulfide in a mixed solvent of water and alcohol (Cf. Roger Adams, "Organic Synthesis" published by John Wiley & Sons Co. Vol. 26, p. 34). Compound 2 and compound 3 are similarly synthesized by reacting the corresponding diamine with carbon sulfide. Compound 4 is obtained by reacting methyl isothiocyanate with N-methyl-ethanolamine in ether, distilling the ether and recrystallizing the residue from ethyl acetate. Compounds 5- 7 are synthesized similarly by reacting isothiocyanate R.sub.1 -N C S with the corresponding secondary amino compound R.sub.2 --NH--R.sub.3.

The amount of the foregoing compound to be added to bleach-fixing solution is from 0.1 g./1. to the minimum dissolving amount of each compound, preferably 0.3 g./1. to 5 g./1. These compounds may be used separately or together.

The acceleration of bleaching reaction by the compound can also be observed when it is added to any of the processing solutions between the color development and bleach-fixing bath in an amount within the range mentioned above.

PREFERRED EMBODIMENTS

The following examples illustrate the amount of color stain produced when the compound mentioned above is added to a color developing solution and the degree of acceleration of bleaching when it is applied, but this invention is not confined to the scope of examples. ##SPC4##

Thiourea (compound 8) and its derivative (Compound 9) that had been used for bleach acceleration in the prior art, and the foregoing Compound 1 to Compound 7 were respectively added to a color developing solution containing N-ethyl-N-.beta.-hydroxyethyl-p-phenylenediamine and dissolved completely. A color printing paper was treated with thus obtained color developing solution to give the following results. Cyan stain was formed in this experiment. ##SPC5##

It is evident from the results that addition of the Compound 1 to the Compound 7 of the invention amounting to 5'.times. 10.sup..sup.-2 g./1. did not result in cyan color-stain while the cyan color-stain occurred in the case of Compounds 8 and 9 even with the smaller amounts, 5.times. 10.sup..sup.-7 g./l. and 5.times. 10.sup..sup.-6 g./1. respectively. This means that, when one of the bleach-accelerating agents (Compound 1-Compound 7) is added to a bleach-fixing solution by the amount of 5 g. per litre, no color stain will be observed even though the bleach-fixing solution is carried over into the color developer to the proportion of 10 ml. bleach per 1000 ml. developer. In this example, the processing temperature was 24.degree. C. and the color developing time was 6 minutes.

EXAMPLE 2

Compounds l- 9 were added to a color developing solution containing N-ethyl-N-.beta.-hydroxyethyl-p-phenylenediamine and dissolved completely. A color positive film was then treated with color developing solutions respectively to give the following results. ##SPC6##

It is evident from the results that the addition of Compounds l- 7 of the invention amounting to 5.times. 10.sup..sup.-2 g./1. did not result in magenta color-stain, while the magenta color-stain occurred in the case of Compounds 8 and 9 even with their smaller amounts, 5.times. 10.sup..sup.-6 g./1. In this example, the processing temperature was 21.degree. C. and color development time was 14 minutes.

EXAMPLE 3

Compounds 1- 8 of example 1 were added to the following bleach-fixing solution by the amount of 2 g. per 1000 ml. respectively. 1,000

11 Iron Salt of EDTA 34 g. Sodium Carbonate (monohydrate) 11 g. Boric Acid 45 g. Sodium Thiosulfate 140 g. Additive 2 g. Water to Make 1,000 ml. pH 6.8

a color paper was exposed, developed, fixed and then passed through these bleach-fixing baths. The times required to remove the developed silver were shown in the table below.

It is apparent from these results that the Compounds 1- 7 of the invention have substantially the same bleach accelerating effect as Compound 8 (thiourea). The processing temperature in this example was 24.degree. C. When a color film was used in place of the color paper, similar results were obtained.

EXAMPLE 4

Compounds 1- 7 of example 1 were added to the following stop fixing solution in an amount of 1 g. per 1000 ml. respectively.

Sodium Thiosulfate 150 g. Sodium Sulfite 15 g. Boric Acid 12 g. Glacial Acetic Acid 15 ml. Potassium Alum 20 g. Additive 0.1 g. Water to Make 1,000 ml. pH 4.3

some test pieces of a color paper were exposed and developed, and then fixed with each of the stop fixing baths containing our compound. Another piece was treated similarly except that it was fixed with the stop fixing bath containing no such compounds for comparison. A clear difference in the bleaching speed between them was found as follows:

It is apparent from these results that when the compounds of the invention were added to a stop fixing bath, they accelerate the subsequent bleach-fixing. In this example, the processing temperature was 24.degree. C. and the stop fixing time was 2 minutes.

As another example of our invention, aqueous solutions of the Compounds 1- 7 were prepared. Some test pieces of a color paper, were exposed, developed, stop fixed, and then processed with the bleach-fixing solution in the same manner as in example 3, but containing no accelerator of our invention after immersing in each of the above aqueous solutions. A clear difference between them in the bleaching speed was found as shown in the following table.

It is apparent from these results that when processed with an aqueous solution of the compound of the invention, the acceleration of bleaching was observed in the subsequent bleach-fixing bath. The processing temperature in this example was 24.degree. C.

When a color film was used in place of color paper, similar results were obtained as expected.

Claims

What is claimed is:

1. In the simultaneous bleach-fixing method of producing color images from exposed photographic color materials using developers which are capable of forming a silver and a color image, and a bleach-fixing bath containing an iron salt of ethylenediaminetetraacetic acid, the improvement which consists of processing said materials at a point later than color development but not later than the bleach-fixing step in a bath which contains as the bleach-accelerating agent a water-soluble compound represented by the general formula: ##SPC7##

wherein R.sub.1 and R.sub.2 each represents a member of an alkyl group, a hydroxyalkyl group, and aryl group and an allyl group, said R.sub.1 and R.sub.2 can form together a heterocyclic ring, and R.sub.3 represents a member selected from the group consisting of an alkyl group, a hydroxyalkyl group and a an allyl group when R.sub.1 and R.sub.2 do not form a heterocyclic ring, and represents a member selected from the group consisting of hydrogen, an alkyl group and a hydroxyalkyl group when R.sub.1 and R.sub.2 form a heterocyclic ring, whereby contamination of said color developers by said bleach-accelerating agent has no substantial color-staining effect during the color development.

2. The method as claimed in claim 1 wherein said compound is one selected from the group consisting of: ##SPC8##

3. The process of claim l wherein at least one processing prior to said bleach-fixing and subsequent to said color development is a stop-fixing process.

4. The process of claim 1 wherein said water-soluble bleach accelerating compound is present in said bleach-fixing bath in an amount of from about 0.3 to about 5 grams/liter.