US1933789A - Photographic developer for use at high temperatures - Google Patents

Description

Patented Nov. 7, 1933 UNITED STATES PATENT OFFICE PHOTOGRAPHIC DEVELOPER FOR USE AT HIGH TEMPERATURES John I. Crabtree, Rochester, N. Y., and John F.

Ross, Phillipsburg, N. J., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New York No Drawing. Application March 14, 1930 Serial No. 435,954

7 Claims.

This invention relates to a photographic developer, especially to one capable of use at relatively high temperatures, and more particularly to one which contains the well known hardening agent, namely, formalin, but which contains a,

The use of formalin as a hardening agent in developers or other photographic baths, especially for use in the tropics or at relatively high temperatures, has been known for many years, there being many references to its use in the literature and textbooks of photography. In the art of photographic developing, temperatures very much in excess of 70 Fahrenheit are usually termed high temperatures and the expression is so used here. When formalin is used in any of the ordinary developers for high temperature work, it usually produces a heavy fog or veiling of the image which is, of course, objectionable. This cannot be overcome by the use of any of the agents usually employed for reducing fog, such as potassium bromide, and the use of formalin for high temperature development has therefore been greatly restricted. This is particularly true of alkaline developing solutions.

We have found it possible to select a developing agent for use in a developer including formalin so that no appreciable fog is produced, even if the solution is alkaline. One of the best developing agents for this purpose is paraaminophenol. Pyrocatechol or monomethyl paraminophenol sulphate may also be used for this purpose. are the halogen substituted hydroquinons as described by Muehler supra. It is only necessary to make up a suitable developer containing one of these substances, together with formalin, to prepare a developer giving the desired results. Development, of course, is carried out in the usual manner after which the plate or film 'is washed and fixed, preferably. in a hardeningfixing bath of a well known type.

In carrying out our invention the formalin may be used in the form of the-40% solution sold on the market, or in the form of dry powdered trioxymethylene' which. with water under the conditions employed yields formalin. Three Other suitable developing agents formula which areillustrative of a number which may be used are:

Formula. Number 1 Para nminophenoL 7 grams Sodium carbonate- 50 grams S0dium-sulphite 50 grams 'irioxymethylene 2 to 10 rams Water to 1 ter Formula Number 2 Mouomethyl paraminophenol sulphate ig Sodium sulphite 75 grams Sodium carbonate 25 grams Potassium bromide 1.5 grams 40% formalin 5 to 25 cc. Water to 1 liter Formula Number 3 Pyrocate 7 grams Sodium carbonate 50 grams Sodium sulpbite ..s 50 grams formalin 5 to 25 cc. Waterto 1 liter All of the above developers are included in the class which normally give little aerial fog and may be considered as fog inhibiting developingagents. However, it has hitherto been known that even at high temperatures and when used with formalin they do not produce fog.

While particularly useful at higher temperatures, the advantages are also inherent whatever the temperature. Formalin is not, however, often used. at lower temperatures. We consider as within our invention all equivalents'and modifications coming within the scope of the appended claims.

What we claim is:

1. A photographic developer including formalin, an alkai and monomethyl paraminophenol sulphate and which, without other elements therein, is substantially free from fogging effects when used at high temperatures.

2. A photographic developer including formalin, an alkali and pyrocatechol and which, without other elements therein, is substantially free from fogging eifects when used at high temperatures.-

3. A photographic developer including-a carbonate of an alkali, formalin and a developing agent selected from the'group consisting of paraaminophenol, monomethyl-paraminophenol sulphate and pyrocatechol and which, without other elements therein, is substantially free from fog ging efiects when used at high temperatures.

4. A photographic developer including formalin, an alkali, and paraminophenol and which, without other elements therein, is substantially free from fogging effects when used at high temperatures.-

5. A photographic developer including forma- 7. A photographic developer including forma- 1m, sodium carbonate and pyrocatechol and which, without other elements therein, is substantially free from fogging effects when used at high temperatures.

l JOHN I. CRABTREE. JOHN F. ROSS.