US2098086A

US2098086A - Photographic desensitizer

Info

Publication number: US2098086A
Application number: US90891A
Authority: US
Inventors: Dieterle Walter
Original assignee: Agfa Ansco Corp
Current assignee: GAF Chemicals Corp
Priority date: 1935-07-25
Filing date: 1936-07-16
Publication date: 1937-11-02
Anticipated expiration: 1954-11-02
Also published as: FR808128A

Description

Patented Nov. 2, 1937 UNl'l'ED STATES PATENT OFFICE 2,098,086 PHOTOGRAPHIC DESENSITIZER No Drawing. Application July 16, 1936, Serial No. 90,891. In Germany July 25, 1935 4 Claims.

My present invention relates to photographic desensitizers.

One of its objects is an improved desensitizing solution. Further objects will be seen from the detailed specification following hereafter.

A good desensitizer should fulfill the following requirements:

1. It should be colorless.

2. It should not be flocculated by the antihalo dyestuff which most photographic materials for amateurs now contain.

3. The anti-halo dyestuff should be nullified in the desensitizing solution, so that the coloring of the bath and possible damage to the photographic emulsion layer may be avoided.

It has been proposed to use for desensitizing sensitive silver halide emulsions, particularly panchromatic emulsions, colorless water-soluble derivatives of anthraquinone or phenanthrenequinone. These compounds have not, however, been introduced into practice as desensitizers, since their capacity in this respect is far below that of the known best desensitizers, especially Pinacryptol green and Pinacryptol yellow.

5 This invention is based on the observation that the desensitizing effect of water-soluble derivatives of anthraquinone or phenanthrenequinone may be considerably increased by using such derivative in a solution which contains at least 2 30 per cent of sodium sulfite, calculated as anhydrous salt. The solution may contain an amount of sodium sulfite up to saturation.

Such a desensitizing solution is equal in its effect to the hitherto known best desensitizers. It

5 also possesses notable advantages as compared with the known desensitizers:

1. The solutions are completely colorless.

2. The desensitizers are not flocculated by the anti-halo dyestufi.

40 3. Owing to the presence of sulfite it is ensured that the anti-halo dyestuff will be nullified in the preliminary bath. This makes it possible for the negative material to be controlled by inspection from the first moments development. Moreover,

45 in this manner diffusion of any photographically injurious anti-halo dyestuii from the non-curlinglayer and its passage into the photographic layer is avoided, a mishap which was possible in the case of the old preliminary baths.

50 These properties are not united in any of the known desensitizing solutions. The desensitizing solutions of this invention fulfill in an ideal manner all the requirements of the case.

This technical eifect is surprising to the ex- 55 pert, for previous knowledge indicated that the derivatives of anthraquinone or phenanthrenequinone are little suitable as desensitizers and they were not used as such. It could not be expected that the use of sulfite would increase the desensitizing effect of these bodies for example 5 by 10 to 15 times (with a content of 4 per cent of sulfite) for it was known that sulfite has a weakening effect, and indeed a destructive eiiect, on numerous desensitizers. It has indeed been found that the desensitizing effect of derivatives of 10 anthraquinone or phenanthrenequinone is not diminished in presence of sulfite, but it has not been observed that the desensitizing effect can be raised by this agent. Thus it was not known that by a definite content of sulfite there would 15 be so high an increase in the desensitizing effect that the action would become equivalent to that of the best desensitizers.

Recipes for suitable preliminary baths in accordance with this invention are as follows: 20 1. Sodium 1-nitro-anthraquinone-7-sulfo nate gram 1 Sodium sulfite grams 40 Water cubic centimeters 1000 2. Sodium anthraquinone-2-sulfonate gram 0.5 Sodium sulfite grams 40 Water cubic centimeters 1000 3. Sodium 1-chloro-anthraquinone-2-carboxylate gram 0.5 Sodium sulfite grams 40 Water cubic centimeters 1000 4. Sodium anthraquinone-Z-carboxylate gram 0.5 Sodium sulfite grams 40 Water cubic centimeters 1000 What I claim is:

1. A photographic desensitizing solution which comprises an aqueous solution of a water-soluble compound selected from the group consisting of an anthraquinone and a phenanthrenequinone, and at least 2 per cent of sodium sulfite.

2. A photographic desensitizing solution which comprises sodium l-nitro-anthraquinone-7-sulfonate, at least 2 per cent of sodium sulfite, and water.

3. A photographic desensitizing solution which comprises sodium 1-chloro-anthra uinone-2- carboxylate, at least 2 per cent of sodium sulfite, and water.

4. A photographic desensitizing solution which comprises sodium anthraquinone-2-carboxy1ate, at least 2 per cent of sodium sulfite, and water.

WALTER DIETERLE.