US1082622A - Development of photographic images. - Google Patents

Description

STATES PATENT OFFICE.

WILLIAM nay CALDWELL, or courier or INVERNES'S, SCOTLAND.

DEVELOPMENT OF PHOTOGRAPHIC IMAGES.

1,082,622. HoDrawing.

To all whom it may concern:

Be 't known that I, IVILLIAM HAY CALD- WELL, a. subject of the King of Great Britain and Ireland, residing in Invernessshire, Scotland,haveinvented Improvements in or -Relating to the Development of Photographic' Images, of which the following is a specification.

In the development of exposed silver haloid films there are three main factors to beta-ken into consideration, namely (a) the amount of' the silverhaloid in the filmthat has, been afi'ected by light, that isto say the number of unit portions of the haloid that havebeen affected; (1)) the amount and nature of the'reducerpresent in the developer and (c) the amount of silver haloid solventpresent in the developer:

With all ordinary developers for bromid fast plates, the reducer issuch that all-dissolved silver bromid present in iIistanta-neously reduced to silver in contact with altered silver salt produced bv exposure tolight with the result that the: whole of thelight affected unit portions of silver haloid :on each grain of the silver haloid present in the film. are not utilizedin bringing about the reduction of the whole grain, one unit alone being sufficient to bring about the reduction of the whole grain so that the image isnot developed in the most perfect manner desirable, especially in the case of With such developers, therefore, the efi'ect'ive workin units are the light affected aggregates of sllver haloid', and since the effective working units are,

compared to the number of molecules present, few in number, the latitude of the plate, as regards exposure, is small. This action is independent of the changes due to exposure in the film as is shown by the fact that the films forming the subject matter of former Letters Patent granted to me No. 956,567 dated May'3, 1910, though incapable of injury through being over exposed, yet, with ordinary, developers, cannot be deaveloped to the same scale of gradations wlth different exposures.

Now the present invention has for its object to develop exposed photographic films with a developer such that the silver haloid,

. TQ -JeXampIe siIVer bromid, dissolved by the developen-shall notbe reduced so quickly as f'ordinary'developerbut shall, on the Specification of Letters Patent.

Patented Dec. 30, 1913.

Application filed June 19, 1912. Serial No'. 704,623.

portions of silver haloid that havebeen af-' fected by light so that silver *haloid in solution shall be reduced to silver in contact with each of'the unit portions, whereby a perfect development ofthe'phot'ographic image can be obtained in the case of films that have had along exposure. For thispurpose I have found that verysatisfactory results can be obtained by developing an exposed film with a solution of a double salt obtained by combining an aromatic hydrazin base and an alkali metal'sulfite, or by using. though not with such good results, the sulfurous acid salt of the base itself. v By these means, the proper function of a perfect developer is fulfilled, namely that the developer should.

C H NH NH,NaHSO In all casesit is essential that the solution be acid to litmus. any alkaline salt, 0. 9., na so is suflicient to destroy the required propertyof the developer; The developer can also be prepared in-the' form of a dry white powder by mixing'the hydrazin base with sodium bisulfite in equal molecular proportions and adding thereto Water in the proportion of 3% molecules.

- In practice it is found that phenyl hy- Even a slight excess of drazin is irritating to the hands of the op erator. By replacing one or mo of the atoms of hydrogen in the para or ortho position in the phenyl nucleus with one or another of numerous available groups or certain elements this disadvantage is found to be overcome. Among suitable inorganic elements or groups may be mentioned chlorin, bromin or HSO, each possessing positive properties, or NH possessing negative properties while a large number of organic groups or radicals as for instance hydro.- carbon radicals such as methyl (0H,),ethyl- (C 11 and so on are suitable. Substances of this character are included in the generic substitution bodies referred to in certain of the claims under the expression anti-corrosive.

By the use of a developer such as described the silver salt in the film is dissolved, transferred across the gelatin or like medium constituting the [ilm and deposited on the whole of the separate light affected units present. the amount of silver reduced and deposited, and hence the density or the image obtained being limited only by the amount of silver present in the film. On the other hand, in the case of an ordinary developer, the amount of silver deposited is limited by the ambunt or" silver reducedby a given exposure and is dependent upon the number of grains of silver haloid affected.

By regulating the strength of the new developer by using more or less water, any desired gradation of the developed image can be obtained by well known laws, because, by altering the quantity of the solvent of the unaltered silver salts, one can vary the rate of solution compared to that of diffusion in the film. Thus, one can starve the high lights and produce a flat result by using more water and vice versa. Further control c anbe obtained by varying the temperature of the developer before use, as this changes the activity of the reducer in the developer.

A suitable stock developing solution can be prepared by dissolving one ounce of the new developer in the state in thirty three ounces of water at a temperature of allowing the solution to.

120 to 150 1?, cool and filtering it. For developing a film having an-over-exposure of '10 to 100 times that technically called. correct, a suitable developer can be made by mixing two parts of the stock solution with one part of water and using the resulting developer at from 70 F. to F., the average time of development being from 20 to 45 minutes. .For de veloping a film having an exposure of from 100 to 1000 times, the stock solution can be used without further.dilution, at a temperature of from 60 F., to 50 F., the rule being the longer the exposure the colder should be the developer. This rate will apply also to abnormal over exposures of say 5000 times and upward, where the temperature of the developermay be lowered to 35 F. These extreme over exposures can be developedat a higher temperature by the addition of solution to the developer solution. I

' The films before development may advan tageously be immersed in a 2% solution of sodium carbonate anhydrous)'for about two minutes, theu in water and the suriacewiped with a pad of cotton wool;

The present invention can advantageously beapplied inthe development of images on photographic films or surfaces-ofthe kind forming the subject matter of my said vformer Letters Patent No. 956567. With these films, any exposure however prolonged, up

to complete printing out, can be develr oped to give the correct scale of density.

What I claim is 1. The herein described improvement in the art of developing a photographic film containing a silver salt, which consists in subjecting the film to a slowly acting developer, acid to litmus, dissolving out thereby silver salt that has been .unacted upon by light andvcausing the dissolved silver salt'to slowly diifuse or travel through the film medium to all the unit portionsot' the silver salt that have been affected by light 'so that silver salt in solution shall be reduced to silver in contact with each of said unit portions substantially as described for the purpose set forth.

2. The herein described improvement in.- the art of developing a photographic ,iilm containing a silver salt, which consists in subjecting the film to the action of a solution, acid to litmus, obtained by combining an aromatic hydrazin base with a compound containing sulturous acid.

3 The herein described improvement in the art of developing a photographic film containing a silver salt, which consists in subjecting the film to the action of'a solution, acid to litmus, of a double salt obtained by combining an aromatic hydrazin base. and an alkali metal sulfite.

4. The herein described improvement in the art of developing a photographic film containing a silver salt, which consists in subjectingthe film to the action of a solution, acid to litmus, of a double salt obtained by combining an aromatic hydrazin base and acid sulfite of sodlum.

5. The herein described improvement in the art of developing a photographic. film containing a silver salt, which consists in subjecting the film to the'action of a solution, acid to litmus, of a double salt obtained by combining a phenyl hydrazin base and an alkali metal'sulfite.

'6. The herein described improvement in the art-of developing a photographic film containing a silver salt, Whichconsists in subjecting the vfilm to the action'of a solution, acid to litmus, of a double salt obtained by combining a phenyl hydrazin base in which an atom of hydrogen in the phenyl nucleus distant an odd number of positions from the hydrazinhas been replaced by an anti-corrosive substance, with an alkali metal sulfi te, substantially as described.

7. The herein described improvement in the art of developing a photographic film containing a silver salt, which consists in subjecting the film to the action of a solu-.

tion, acid to litmus,-of a double salt obtain ed which an atom of hydrogen in the phenyl nucleus has been replaced bya halogen, with an alkali metal sulfite.

8. The herein described improvement in the art of developing a photographic film containing .a silver salt, which consists in subjecting the film to the action of a solu-] tion, acid to litmus, of 'a double salt obtained I by combining a phenyl hydrazin base in which an atom of hydrogen in the ortho' position in the phenyl nucleus has been-replaced by an anti-corrosive substance, with an alkali metal sulfite.

9. The herein described improvementint'h art ofdeveloping a photographic film' containing 'a'silver salt, .which consists in.

subjecting the fil-mto the action of a solution, acid to litmus, of a double salt obtained" by combining a phenyl hydrazin base in which an atom of hydrogen in the phenyl nucleus distant an odd number of positions 'from the hydrazin has been replaced by bromin,'with an alkali metal sulfite.

10. The herein described improvement in the art of developing a photographic film containing a silver salt, which consists in subjecting the film to the action of a solutiomacid to litmus, ofa double salt obtained by combining ortho-brom-phenyl-hydrazin.

with an alkali metal sulfite' 1 1.The herein described improvement in the art of developing a photographic film" containing. a silver salt, which consists in.

subjecting the film to the action 'of a solution, acid to litmus, of a double salt obtained by combining ortho-brozn-phenyl'hydrazin' with acid sulfite of sodium.

12. For developing photographic ,films containing afsilver salt, adeveloper comf prising an aromatic hydrazin base and an .acid sulfite'of an alkali metal. V

13. Forvdevelo-ping photogra hic films containing. a silver salt, a deve oper corn prisingla phenyl hydrazin base in which an atom of hydrogen in the phenyl nucleus at distant an odd number of positions from, hydrazin, -has been replaced by an ant "corrosive substance, and an acid sulfite of an alkali inetal.

1-4. For developing photographic films containing a silver salt, a developer com-' prising ortho-brom-pheny1 hydrazin and an acid sulfite of an alkali metal. 15. For developing photographic films containing a silver .salt, -a liquidd'eveloper comprising an aqueous solution, acid. to litmus, ofa hydrazin base and an acidsulfite ofan alkali metal in equal molecular proportionsp' .16. For developing photographic films containing 'a sil'ver salt a solution comprising .a substitution product,-'in the phenyl nucleus, of phenyl 'hydrazin, said solution being acid