US2081481A - Process for the production of natural colored images on paper and diapositives - Google Patents

Description

Patented ay 25, 193? Richard Gschiipf and Karl Pokorny, Vienna, Austria; said Pokorny assignorto said Gschiipf No Drawing. Application January 10, 1934, Serial No. 706,128. In Austria July 22, 1933 6 Claims.

This invention relates to the production of colored prints, and natural colored images on paper anddiapositives (cinematographic films). A number of processes are known for the production of natural colored prints.

Apart from the colored pictures (autochromatic prints) obtained with screen elements (additive methods) there are only the subtractive methods available for the production of natural 10 colored prints.

In thelatter methods gelatine printing mat rices (swelling and washing out relief) are as a rule produced from the three componentnegatives, and these matrices have hitherto been colored with the normal commercial acid and basic dyes, and then squeegeed one upon the other onto a common image carrier coated with gelatine.

The acid dyes pass over imperfectly and also very slowly from the gelatine printing matrices to the image carrier. This involves great drawbacks, the obviation of which has been attempted by the employment of basic dyes.

The basic dye-stuffs pass over rapidly from the gelatine printing matrix (relief) to the image carrier. However, they are apt to .run and spread in the gelatine layer of the latter.

However, if image carriers be employed the gelatine layer of which is provided with precipitants for these dyestuffs, the matrices bleed,

that is to say they part with the absorbed coloring matter so rapidly during the squeegeeing onto the image carrier, that it forms on the entire surface of the latter a thin insoluble dye 5 compound which also tones the colorless portions 7 that no bleeding out of this matter occurs.

According to most recent knowledge, an important part is played in connection with the coloring of gelatine with dyestufl? by the chemical process (cf. report on paper read by E. R. Bul- 55 lock to the Faraday Society, given in The Physical Chemistry oi the Photographic Process, May, 1923, pages 396-401).

By efi'ecting chemical combining of the dye in the gelatine of the printing matrix, the arbitrariness of the absorption and giving up of the 5 color is not overcome, and all that is actually effected is to render the yielding up of the coloring matter more difficult than otherwise. But also the chemical process occurring in the course a of color transference points to the fact that the 10 basic dyes are unsuitable as such for the production of colored pictures. The base of the dye combines with the mordant or precipitant used (silicotungstic acid, phosphotungstic acid, or the like) as an ingredient of the material of the im- 5 age carrier, while the liberated acid of the basic dye exerts a deleterious influence on the matrix by imparting acid character to the gelatine layer which tends to counteract all further coloration.

Finally, such dye becomes most firmly an- 20 chored in the colloidal structure of the gelatine as is of a molecular size suited to this structure.

, It will be clear from what has been said above that firm adherence of the dye to the gelatine of the matrix, without chemical combining, can only be attained if the dye be in colloidal solution, be freed from acid, and be caused to be of a molecular size best suited for coloration, that is to say if pure dye bases be employed for the coloration. 30

With the employment of this variety of the usual basic dyes itis a simple matter to avoid all the drawbacks attendant upon the use of the two other varieties.

Thus in accordance with the invention, instead of sulphuric acid, hydrochloric acid, acetic acid and other salts of dye bases, there are employed colloidal solutions of dye bases for the coloration of the matrices (reliefs).

These solutions have the property of adhering 4o relatively firmly to the gelatine relief, and that without chemical combining, and nevertheless of passing over extremely rapidly (given suitable treatment of the image carrier in some seconds) and perfectly quantitatively, that is to say without remainder, into the image carrier provided with precipitants.

The preparation of the colloidal dye bases in solution is extremely simple; a suitably concentrated dye solution 0! the basic dye-stud concerned, for example thionine blue, is prepared, and to this there is added, for example, ammonia in such quantity and until the solution is of strongly alkaline reaction, that is to say until the dye base has been liberated.

However,- there also exist basic dye-stuflsthe colloidal dye base solutions of which produced with ammonia begin to separate out in a comparatively short time in the form of a flocculent precipitate, and which are consequently unsuitable for the coloring of gelatine reliefs when merely used in this manner.

Now this can be prevented by adding pyridine, its derivatives, and homologues to the dye-stufi solution or' to the colloidal dye base solution produced by the addition of ammonia.

Whether the pyridine or substances of a pyridine-like nature form complex compounds with the colloidal solutions of dye bases is in this connection of subsidiary importance. It is a fact that an addition of pyridine results in perfectly clear solutions of a colloidal nature of the majority of dye bases, which solutions do not yield fiocculent precipitates. f

In the case of basic dye-stufis of which the colloidal dye base solutions yield fiocculent precipitates even with the treatment specified above, it is further necessary to add to the solutions certain protective colloids such as clextrine and the like, and to remove the salts, such as ammonium nitrate, ammonium sulphate, and the like formed by the alkalies, by dialysis. For example, in order to obtain a free dye base of new solid green which does not flock out, there is added to a solution (of approximately 1% strength) of this dye-stufi, approximately 0.1% of dextrine as a protective agent, and approximately 1 ccm. of pyridine, after which this solution is then treated as specified above.

Where intensification of the alkaline reaction is desired, it is apparent that a substance of alkaline reaction may be added to thecolloidal solutions of the dye bases, if desired.

We claim:

1. A process for the production of single and multicolored prints, consisting in coloring photographic gelatine printing matrices by means of colloidal solutions of dye bases, and transferring the absorbed dye base to a carrier provided with precipitants' 2. A process as defined in claim 1, wherein a substance of alkaline reaction is added to the colloidal solutions of the dye bases for intensifying the alkaline reaction.

3. A process as defined in claim 1, wherein the colloidal solutions of dye bases are produced with the aid of pyridine.

4. A process as defined in claim 1, wherein protective colloids are added in small quantities to the colloidal solutions of the dye bases.

5. A process as defined in claim 1, wherein the colloidal solutions of dye bases are produced with the aid of derivatives of pyridine.

6. A process as defined in claim 1, wherein the colloidal solutions of dye bases are produced with the aid of homologues of pyridine.

RICHARD GscH6PF. KARL POKORNY.