US2472631A - Palladium complexes as photographic emulsion stabilizers - Google Patents

Description

Patented June 7, 1949 TENT OFFICE PALLADIUM COMPLEXES AS PHOTO- GRAPHIC, EMULSION STABILIZERS Robert E. Stauifer and William F. Smith, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application March 5, 1948, Serial No. 13,352

This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions and to photographic emulsion-s containing them.

It is known that photographic emulsions, particularly ultra-sensitive emulsions or those containing optical sensitizers exhibit a tendency to form upon development a deposit of silver in the emulsion. This deposit extends more or less uniformly over the entire emulsion and is known as fog. Photographic fog is of two types: local and general. Local fog is formed by exposure of the film or plate at undesired points as by a light leak in the camera. General fog is formed in a number of ways. It may be caused by. the

conditions under which the film or plate is stored,

such as conditions of high temperature or humidity or unusually long time of storage. The nature of the emulsion may also produce general fog as well as the conditions of development of the emulsion as by development for protracted periods of time or at temperatures above normal. We are primarily concerned with fog and sensitivity changes produced in films or plates on development after storage under adverse conlcjitirons of high temperature and humidity or General fog and loss of sensitivity of the emulsion are especially likely to occur when the sensitive material is stored under conditions other than ideal, that is, under conditions of high temperature and humidity as in tropical regions.

It is an object of the invention to provide novel anti-fogging or fog-inhibiting compounds for emulsions. A further object is to provide antifogging agents which stabilize the initial sensitivity of the emulsion. A still further object is to provide anti-fogging agents which improve the keeping of the emulsion in tropical regions. Other objects will appear from the following description of our invention.

' These objects are accomplished by incorporating in a silver halide emulsion an anionic palladium complex salt such as alkali metal or alkaline earth metal thiocyanato palladites, nitritopalladites, bromo-nitritopalladates, and ammonlum nitritopalladite. For example, we may use potassium thiocyanato palladite, mPd(CNS)4; calcium thiocyanato palladite, CaPd(CNS)4; potassium nitrito palladite, K2Pd(NO2)4; barium nitrito palladite, BaPd(NO2)4; potassium bromonitrito palladate, K2PdBr2(NO2)4, or ammonium nitritopalladite, (NH4)2Pd(NO2)4. Other similar anionic palladium complexes which have not been satisfactory, particularly because of fog- 5 Claims. "(01. 95-7) -2 ging properties or desensitizing action on the photographic emulsion include ammonium and potassium cyano palladites and ammonium thiocyanato palladite.

The object of our invention is to maintain the sensitivity and fog of silver halide emulsion at or close to initial optimum values under keeping conditions of high temperature and humidity. The fog inhibitors which we propose to use are added to the emulsion during the process of manufacture to avoid loss of sensitivity and to inhibit the growth of incubation or keeping fog with passage of time under non-ideal conditions of storage.

A solution of the compounds of the invention when added in suitable concentration before coating to unsensitized or optically sensitized photographic emulsions does notaiiect appreciably the sensitometric values for sensitivity and fog when measurements are made soon after coating. When sensitometric measurements are made after appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures, however, the compounds stabilize photographic speed and in certain cases maintain fog at a low level.

-The preparation of silver halide emulsions involves three separate operations, (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from excess soluble salts usually by washing, (3) the second digestion or after-ripening to obtain increased sensitivity (Mees, The Theory of the Photographic Process, 1942). We prefer to add the fog-inhibiting agents after the final digestion or after-ripening although they may be added before digestion. The most useful concentration range of fog inhibitor is from 0.26 to 3.9 gm. of fog inhibitor per kilogram of silver nitrate used in making the emulsion and converted to silver halide. This amount will vary, e. g., depending upon the particular silver halide used.

'- The antifoggant and stabilizing action was determined by incubation of the emulsions under simulated tropical conditions and also by incubation in dry heat at F. for various lengths of time from 6 days to 2 months. The results of these ageing tests are tabulated below and are compared with the initial speed, gamma and fog of the emulsion without th stabilizing compounds. The tests from which the following tabulation was made used a high-speed orthochromatic negative type of emulsion exposed on an EastmanfI ype sensitometer' and develq oped for five minutes in a developer of the following composition:

Water to one liter.

The results of the comparative tsfi -are as It will be noted from the data in the above table that the improvement in fog and speed stability using the compounds of the invention is appreciable as compared with emulsions containl-ii'g'ho inhibitor. Anothefadv'antage'of our invention is that the compounds may be prepared easily and with high purity compared to organic types of inhibitors. Another and perhaps chief advantage -'is 'the"greater extent of stabilizing whomever-'11: wide range of climatic conditions.

In use, the fog inhibitor is dissolved in water follows:

Original Y Gdays 12min Gms. of compound er Kg.AgNs (con- 1G2 verted to Ag )inemulston H 10/1 G F Gamma Fog Speem I ammo. og

None -,1,15o; 1.11, .12, 590 1.42 .16 K1Pd(CNS)4, 1.250... 91D; 11 1.29 .12 175 1.42 .16 KzPd(NO7)4 1.250. 795 1.35 .16 650 1.43 .24 KzPdBmNm, 1 910 1. 21 .14 710 1. 39 19 Nodal-"0145.- Slbff i.3(5)? 1 1 1 N .PdN. 411? .4-..1, EN i 1,500- 1 1.15 .13= 725- 1.35 .15

1 Control test sample for samples 6 and 7.

Examples of the method oi preparatiomand use of the compounds orthemvehuta are-elven 40 The compound was added to the emulSiondn'the-" quantity shown in the tabla above and the emiilsion containing the usual 'hardener and 1 sensitizew was coa'ted on a glass*plate driei exposed and developed. Other' 'sam'ples of the 'eniuIsi'On were aged and processed with =the results shown in the above 'table. M

Ebz'ampl' 2 Potassium nitrito 'paniaditew'as" prepared one yellow crystals bji reacting 'a'" solut on" or emulsion and tested "with" the results snow-11' i1? 0 the table above."

Ezdviifil '3 Ammonium nitritopal-lad-ite was--prepared gby reactingammonium hexachloropalladateywith-asolution of potassium nitriteand'aminonium chlo ride and after incorporation-Auto anemulsion was tested with the results showfi' inthe "tatile'."

Example-'4 Potassium bromo-nitiitopanaaate was prepared" 1 n'riepr nafec mina-iw 1 ata colnvenient concentration and added to-a melted el'atino-silver halide photographic emul-"- sion-in quantities ranging-up =to about 3. gms/ perkilogra rrrof silver nitrate converted to silver" halide. The emulsion is coated ona suitable supv 1 por-t, glass;-fi1m,- or -other,- and dried inanormal fashion; 7 I

We'also contemplate as a part of our invention those cases where its desirable-to coat theantifog'gant in a colloid layer such as'gelatin on either or both sides of or also in the silver halide emul si'on layer so that the anti-foggantis inat least one=of the-layers. In 'these cases, we'use the same or a slightly greater ratio of rare metal-- salt to silver halide than whenthe salt is in cue-1111 11151011 layer. That is, the inhibitingcomeuna's". maylbe used in a colloid layer-suchasa geiauri' subbin'gor overcoating layer contiguous" tofadJ'acent to, or n contact with the emulsionla'yei'. When used -in this way; the compounds stabili'z'e'thfe emulsiori'when it is aged over long periods of time especially under non-ideal con-- ditibris'of temperature and humidity. In such"- cases theamount of the compound per unit area should be the -same; per kilogram" of silv'er nitifat convertedt silver halide, as would be used 3 ili'tll' saini'llfiit' area of the emulsion if'the com pouriaweredn the emulsiofi'la'yerl v The fog' inhibitih'g ,age'rits' whichwe have' de-" scribed" may .bdu'sed iii va ious kinds of hoto graphic emulsions. Inadditiori" tdbeing useful in ordinary non sens'itized emu'lsio'r'isthey may alsojbe' 'j used" in 'orthochromatic; anchromatic; and x r ay emulsions. If 'used WitHsensiti Zing' dySZ they may be added the emulsionbefore "after th'fdyes' aread'ddf Varioussilver"salts of these. The dispersing agents may be gelatin or other colloid such as collodion, albumen, cellulose derivatives, or synthetic resins.

It will be understood that we contemplate as included within our invention all modifications and equivalents falling within the scope of the appended claims.

What we claim is:

1. A silver halide emulsion containing an anionic palladium complex salt selected from the group consisting of alkali metal and alkaline earth metal thiocyanato palladites, alkali metal and alkaline earth metal nitritopalladites, alkali metal and alkaline earth metal bromo-nitritopalladates and ammonium nitritopalladite.

2. A silver halide emulsion containing an alkali metal thiocyanato palladite.

3. A silver halide emulsion containing an alkali metal nitritopalladite.

4. A silver halide emulsion containing ammonium nitritopalladite.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,120,429 Willis Dec. 8, 1914 1,120,580

Willis Dec. 8, 1914