US2122599A - Photographic developers - Google Patents

Description

Patented July 5, l938 UNITED sTATEs 2,122,599 7 PHOTOGRAPHIC DEVELOPERS Gustav Wilmanns, Wolfen (Kreis Bitterfeld) and Wilhelm Schneider, Dessau (Anhalt) Germany, assignors to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York Nb Drawing. Application December 16, 1936, Serial No. 116,236. In Germany December 23,

16 Claims. (o1. 95-8) 7 The present invention relates to photographic developers. 4

One of its objects is a developer for photographic silver halide emulsions by which the 5 silver halide is transformed into silver. Without previous exposure. Another object is a photographic developer for the reversal process. Further objects willbe seen from the detailed specification following hereafter.

For many purposes, for instance for reversal development, it is often desirable that the second development should be possible without previous exposure to light; for example, when the film has been developed in a bath it is troublesome to 15 have to remove the wet film from the bath, ex-

pose it to light and return it to the bath. It has been proposed to avoid this exposure by using as an equivalent expedient certain reducing substance, for instance hydrosulfite, thiosinamine or 20 the like. Such reducing agents, however, are generally of very low stability and cannot be preserved; in addition theyhave other disadvantages', for instance a disagreeable odour.

The present invention relates to a method for avoiding the foregoing difllculties by using a new namely developers which contain in'the molecule an atom grouping COCHOH or in tautomeric form COH=COH. This atom 30 grouping may be in an open chain or in a heterocyclic nucleus. Such substances are, for example benzoin which may contain various substituents in the nucleus, dioxindols, 2,3 dihydroxythionaphthenes. These substances'may be used either 35 alone or in admixture with normal developers.

. The mixed developers have the property of developing first small silver nuclei which then, after this initial development, are further developed by the normal developer.

40 The following are examples of suitable developers:

I. Dioxindol grams 2 Su1flte -do 10 45 Potassium carbonate do 6 Water cc 200 II. Benzoin sulfonic acid grams' 2 Sulflte do 10 Sodium hydroxide do 0.6 Water cc 200 III. Dioxindol grams 2' Hydroquinone do 10 Sulfite do 50 Potassium carbonate do 30 55 Water "cc 1000 IV. 2,3 dihydroxythionaphthene v c rams 2 Sulflte h do 10 Potassium carbonate do 6 60 Water cc..'

group of developers for the purpose in question,

When an unexposed film is developed in any of these developers there is produced in -10 minutes of developing period. a complete blackening.

What we claim is: 1. In a process of producing reversal images in exposed silver halide emulsions the step which \comprises carrying out the second development without exposure between first and second development by means of a developing bath the active component of which is formed bya compound selected from the group consisting of benzoines, dioxindoles and 2,3 dihydroxythionaphthenes.

2. In a process of producing reversal images in exposed silver halide emulsions the step which comprises carrying out the second development without exposure between the first and second development by means of an ordinary developing bath containing'a compound selected from the group consisting of benzoins, dioxindoles and 2,3 dihydroxythionaphthenes. I

3. In a process of producing reversal images in exposed silver halide emulsions the step which comprises carrying out the second development without exposure between first and second development by means of a. developing bath comprising a'dioxindol.

' 4. In a process of producing reversal images in exposed silver halide emulsions the step which comprises carrying out the second development without exposure between first and second development by means of a developing .bath comprising a 2,3 dihydro'xythionaphthene.

5. In a process of producing reversal images in exposed silver halide emulsions the step which 7 comprises carrying out the second development without exposure between first and second de-,- velopment by means of a developing bath comprising a substituted benzoin.

6. In a process of producing reversal images in exposed silver halide emulsions the step which comprises carrying out the second development without exposure between first and second development by means of a" developing bath having the following composition:

Dioxindol "grams" 2 sulfite I. do 10 Potassium carbonate do 6 Water cc 200 2,3 dihydroxythionaphthene grams 2 Sulfite do 10 Potassium car do 6 water or 200 In a' process of producing reversal images in 6 opment by means of a developing bath having the following composition:

Benzoin sulfonlc acid grams 2 Bulnte do 10 10 Sodium hydroxide do 0.6 Water 200 9. A photographic, developing bath for silver halide emulsions comprising a compound selected from the group consisting of benzoins, dioxindoles and 2,3 dihydroxythionaphthenes.

'10. A photographic developing bath for silver halide emulsions having as the active component a compound selected from the group consisting of benzoins, dioxindoles and 2,3 dihydroxythlonaphthenea.

11. A photographic developing bath for silver halide emulsions comprising a dioxindol.

12. "A photographic developing bath for silver halide emulsions comprising a 2,3 dihydroxythionaphthene'.

13. A photographic developing bath for silver halide emulsions comprising a substituted benzoin.

14. A photographic developing bath for silver halide emulsions having the following composition: v

Dioxin n rams" 2 Sulflte do 10 Potassium carbonate do 6 Water- 200 15. A photographic developing bath-forsilver halide emulsions having the following composition:

2,3-dihydroxythionaphthene grams 2 Sulflte -:lo 10 Potassium carbonate do 6 Water 200 16. A photographic developing bath for silver halide emulsions having the following composition:

Benzoin sulfonic acid grams 2 Sodium hydroxide dn 0,

Water 200 GUSTAV WILMANNS.

WILHELM SCHNEIDER.