US2598079A

US2598079A - High-speed photographic silver halide emulsions supersensitized with palladium salts

Info

Publication number: US2598079A
Application number: US47108A
Authority: US
Inventors: Robert E Stauffer; William F Smith
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1948-08-31
Filing date: 1948-08-31
Publication date: 1952-05-27
Anticipated expiration: 1969-05-27
Also published as: GB659033A; DE964561C; BE490866A; FR1007305A

Description

FIG].

FIG.2.

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UFFER ET AL OGRAPHIC SILVER HALIDE EMULSIONS SUPERSENSITIZED WITH PALLADIUM SALTS Filed Aug. 31, 1948 A REC/PROC/T) CURVE FOR EMULSION SENS/T/ZED WITH POWS/UM CHIOROAURATE AND v JOB/UM THIOCVANA TE AND F/N/JHED 7'0 $0MEWHAT BELOW OPTIMUM SPEED B= REC/PROCI TY CURVE FOR SAME EMULi/ON CONTAIN/N6 PUTASJ/UM CHIOROPALLADATE C= REC/PROC/TY (UKVE FUR SODIUM THIOCX4NA7 AND we 1 (mc) Z0 FINISHED 7'0 OPTIMUM SPEED EMULFlU/Y JfNS/TIZED WITH POTASSIUM CHZORO/IURATE AND 1; REC/FRONT) cum 5 FOR SAME EMl/U/flN (OHM/NINE Poms/UM CHLOROPALMDATE ROBERT E.S724UFFER WILLIAM F. SMITH JNVENTORS fid A TTORNEYS Patented May 27, 1952 HIGH-SPEED-PHOTOGRAPHIC SILVER HAL- IDE EMULSIONS. SUPERSENSITIZED.WITH PALLADIUM SALTS Robert E. Staufier as William F. Smith, Roch ester, N. ,Y,, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey ppli a n us 94.8, SerialNo. 47;.108 15 Claims. (01. 95-7) v This invention relates to high speed photographic silver halide emulsions supersensitized with palladium salts.

It is known that high speed photographic silver halide emulsions can be prepared by incorporating in the emulsions labile sulfur sensitizing bodies or gelatins and/or gold compounds. We havenow. found that such high speed emulsions canbe supersensitized by adding to them a palladium salt. Thus, the emulsion can be brought tomaximum sensitivity with the gold compound and then be rendered still more sensitive with the palladium salt, or the emulsion can be brought to a sensitivity short of the maximum sensitivity attainable with the gold compound and then. be rendered more sensitive with the palladium salt. In addition, we have found that the palladium salts act as sensitizers for the low intensity portion of the reciprocity curve of such emulsions sensitized with gold compounds.

It is, accordingly, an object of our invention to provide new supersensitized high-speed photographic silver halide emulsions. A further object is to provide a process for preparing such emulsions. Other objects will become apparent hereinafter.

In accordance with our invention, we incorporate' in a high-speed silver halide emulsion which is sensitized'with at least one gold compound and/or at least one sulfur sensitizer, at

least onepalladium salt. The high-speed silver halide emulsions sensitized with at least one gold compound, can be prepared by incorporating at least one gold compound in a photographic silver halide emulsionat any stage of the preparation ofthe emulsion or, when the emulsion iscomplated, e. g. just'before coating of the emulsion. The gold compound is advantageously employed in a concentration equal to not more than 0.015 per cent by moles of the silver halide in the emulsion, and in the case of gelatino-silver-bromide (including the so-called bromoiodide emulsions ofwliich the majority of the halide is bromide, with a few per cent of iodide), the upper limit is advantageously 0.01 per cent by moles. Up to 0.015 percent by moles-of the silver halide in the emulsion, the-amount of, the gold compound can vary widely, as perceptible effects can be obtained with 0.0003 per cent or less. Advantae sly, the lower limit is about 0.001 per cent by moles of the, silver halide in the emulsion. We havefound that from 0.003 per cent to about 0.005 per cent by moles is advantageously employed in practice, especially when the gold compound is incorporated in the emulsion during the. preparation of the emulsion, i. e. especially when the emulsion is digested in thepresenceof the gold compound.

The gold compounds can be added to theemlllsions at any stage of thepreparation of the emulsions, i. e. before or during precipitation of the silver halides, before or during the first digestion (ripening) of the emulsion, beforeor during the second digestion of the emulsion, or the gold compounds can beadded to the emulsion J'ust beforecoating the emulsion. The gold compounds are advantageously incorporated in the emulsions in the form of their solutions in a suitable solvent, e. g. water, methyl alcohol, ethyl alcohol, etc.

The gold compounds which we have found are most advantageously employed in preparing .the high speed emulsions are the gold halides, such as auric chloride, or complex gold halides, Such as potassium chloroaurate (KAuCli) and sodium chlorcaurate (NaAuCll). However,. gold compounds, such. as auric sulfate, are practically as useful as the, gold halides. Aurous, as well as auric compounds can be used. Complex. gold salts, such as alkali metal aurous thiosulfates, alkali metal aurous sulfites (e. g. sodium or potassium aurous thiosulfate and sodium or potassium aurous sulfite), and a complex salt formed by the interaction. of thiourea and auric chloride, are also suitable. Potassium chloroaurite, potassium bromoaurite, potassium iodoaurite, potassium auricyanide, potassium aurithiocyanate or the corresponding sodium, calcium, strontium, cadmium or gallium salts can alsobe used. Pyridinotrichloro-gold, ethylenediamine-bis-trichlorogold, diethyl-monobromo-gold and diethyl gold acetone and gold complexes with sulfur compounds'such as are commonly present in gelatin, e. g. the gold thiosinamine complexes, canalso be used.

Sulfur sensitizers are advantageously also added to the emulsions. Gelatins normally contain certain sulfur compounds which act as sulfursensitizers of" photographic emulsions, but beneficial efiectsa're obtained in accordance with our invention by adding sulfur sensitizers, i. e. sulfur compounds containing C=S groups or SS- groups, e. g. thiourea, allyl isothiocyanate, thiosinamine (allylthiourea) etc. Beneficial efiects are also obtained byadding metal or ammonium thiocyanates, e. g.,sodium, potasslum, ammonium, calcium or cadmium thiocyanates, to the emulsion. of course, .thiocyanates containing cations which cations areknown to h v in themselves, a del terious effect on silver halide emulsions should be avoided. Otherwise the beneficial eiiects of the thiocyanate would be partially nullified by the deleterious efiect of the cation. Thus, iron thiocyanate should be avoided. One or more sulfur sensitizer can be employed, and one or more thiocyanates selected from the group consisting of metal and ammonium t-hiocyanates can be employed in conjunction with a sulfur sensitizer other than a thiecyanate containing a cation selected from the group consisting of metal and ammonium cations. The sulfur sensitizers are advantageously incorporated in the emulsions in the form of their solutions in a suitable solvent, such as water, methyl or ethyl alcohol.

The sulfur sensitizers can be incorporated in the emulsions at any stage of the preparation of the emulsion, e. g. during the precipitation of the silver halides, during the first digestion (ripening) or during the second digestion of the emulsion. When incorporating thiocyanates in the emulsions prior to washing the amount can vary widely. Advantageously, however, an

amount of thiocyanate equal to from about 2 to about 15 per cent by moles of the silver halide in the emulsion is advantageously employed. If the thiocyanate or other sulfur sensitizer is not added until later in the preparation of the emulsion, e. g. after washing, it is advantageous to employ an amount equal to from about 0.1 to about 2.5 per cent by moles of the silver halide present in the emulsion in the case of metal and ammonium thiocyanates, and an amount equal to from about 0.006 to about 0.06 per cent by moles of the silver halide in the case of other sulfur sensitizers.

It is advantageous to digest, i. e. heat treat the emulsion with the gold compound with or without the sulfur sensitizer, at an appropriate temperature, e. g. at from 100 to 150 F. During digestion, i.e. the second digestion as contrasted with the first digestion or ripening, the pH of the emulsion is advantageously adjusted to the acid side of neutrality, e. g. between 5 and 7. Maintenance of the emulsion on the acid side of neutrality during coating of the emulsion is also advantageous.

. The palladium salts which we employ in practicing our invention can be represented by the following general formulas:

MzPdXs and MzPdX4 wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms. Typical of such palladium salts are: ammonium chloropalladate, potassium chloropalladate, sodium chloropalladate, ammonium chloropalladite, sodium chloropalladite, potassium bromopalladate, potassium iodopalladate, etc.

The palladium salts are advantageously added to the emulsion just before coating the emulsion, but can be added at any time to the finished emulsions. One or more of the palladium salts can be used. The palladium salts are advantageously incorporated in the emulsions in the form of their solutions in a suitable solvent, e. g. water, methyl alcohol, etc.

The palladium salts are advantageously employed in a concentration of from 0.015 to 0.2 per cent by moles of the silver halide in the emulsion. Usually from 0.3 to 0.15 per cent by moles produces the maximum supersensitizing effect.

Palladium salt, ercent by moles of Speed silver halide in the emulsion) Gamma Fog 110118 (N H4) 2PdC1c(0.05) (NH4)2Pd 0140.05) KzPdChfllOfi) Example 2 A high speed photographic gelatino-silverbromide emulsion of the negative type sensitized with potassium chloroaurate (KAuCh) and sodium thiocyanate was prepared and finished to optimum speed. Potassium chloropalladate was added to the emulsion. The emulsion was coated on a glass plate, the coated plate dried and then tested in a sensitometer, development being at 68 F. for 5 minutes in Eastman Kodak Companys BK-50 developer. Results were as follows:

Potassium Ohloropallate. (percent by moles of silver halide in the emulsion) Gamma The palladium salts act to sensitize the emulsions sensitized with the gold compounds, for the low-intensity portion of the reciprocity curve. For many purposes, such as astronomical and spectroscopic photography, it is useful to have photographic emulsions showing a low reciprocity failure at low intensities. The effect of the palladium salts in this respect is apparent from the curves in the accompany drawing. Fig. 1 shows reciprocity curves for the emulsion of Example 1 (with and without KzPdCls) in which log I (meter candles) is plotted against log It (meter candle seconds) (density:l.0+fog) in the manner customarily employed to illustrate reciprocity law failure (see The Theory of the Photographic Process, C. E. K. Mees, page 242, MacMillan Company, New York, 1942). Curve A represents the emulsion without the palladium salt and curve B represents the emulsion with the palladium salt. It will he observed that the emulsion containing the palladium salt shows distinctly lower reciprocity failure at low intensities than does the emulsion without the palladium salt, curve B'curving upwards only at about 10 seconds, while curve A shows an upward slope at less than second exposure. The ideal, of course, would be a straight-line curve throughout the entire range of exposures.

Fig. 2 shows reciprocity curves for the emul sions of Example 2, (with and without KzPdCls) in which log I is plotted against log It (dentitreingside) :1. Crime (3. in Fig. 2 represents the emulsion without the palladium salt and curve D. represents the emulsion with palladiumisalt. It.:wil1'.be observed that .theemul- .sionj containing, the palladium salt shows distinctly lower reciprocity failure especially at the lower intensities.

The emulsions prepared in accordance with Our-invention canhecoated in-therusual manner on supports such as. glass, photographic film base, e. g. cellulose. acetate type, photographic paper-base, etc. Sensitizing .dyes of: all types can be employed to spectrally sensitize our new emulsions, e. g. erythrosin, .Congo'Red, any of the sensitizing oya-nine dyes, any of the sensitizing merocyanine dyes v(see United States Patent 2,078,233, dated April '27, 1937, forexamplez, any of thesensitizing 'hemicyaninedyes (see United StatesIPa-tent 2,166;736, dated July 18, 1939, for example) and of thesensitizing hemioxonol dyes (see United States Patent 2,165,339, dated July 11,1939, for example), etc.

Our invention is directed primarily to the customarily employed photographic silver halide developing-out emulsions, e. g. silver chloride, silver chlorobromide, silver chlorobromoiodide, silver bromide and silver bromoiodide developingout emulsions. A suitable gelatino-silver-halide emulsion is described, for example, by A. P. H. Trivelli and W. F. Smith, Phot. J. 79, 330 (1939). Such an emulsion can be prepared as follows:

In a container equipped with a temperature control was put a solution of the following composition:

A. potassiumv bromide Mug 825 gelatin ,ig 325 Water cc 8,500

and' in another container was put a solution consisting of:

B. silver nitrate g 1,000 water cc 10,000

Solution A was kept at a temperature of 70 C. and solution .B was put in a separator-y funnel at a temperature 015172 C. Solution B was allowed to run, in minutes, from the separatory funnel through a calibrated nozzle into solution A which was kept in constant motion during the precipitation of the silver halide. After precipitation of the silver halide, the resulting emulsion while being kept in constant motion was ripened for 20 minutes at 70" C. Then, the emulsion was cooled as quickly as possible to C. and at this temperature, 1250 g. of washed gelatin were added to the emulsion. The emulsion was stirred for 20 minutes at 45 C. in order to dissolve the gelatin. After standing overnight in a cold storage room (10 C.), the emulsion was shredded and washed. It was then melted at a temperature of 42 C. Theweight of the emulsion was brought to 31.5 kgs. by adding 500 g. of gelatin soaked in the required amount of distilled water. The emulsion was then finished at C. to the desired speed, in the presence of one or more'gold compounds and one or more sulfur sensitizers (see Examples 1 and 2).

The sensitization of photographic silver halide emulsions by meansof gold compounds-alone, or with sulfur sensitizers is well known in the-art.

What we claim as" our, invention and desire to be secured by Letters Patent of"the- United States is:

l. A high speed photographic silver halide emulsion sensitized with at least one gold compound; in. a conoerltrziltionv equalzto 00003111130 0;015% by males of the silver hElj-dkliilrithfi emulsion, said emulsion. containing. as a supersensitizer, at least one palladium salt. selected from the group consisting of. 'palladium salts represented by the following, general formulas:

wherein M represents a member selected from the group consisting .of an alkali metal atomand an ammonium radical, andX represents a. halogen atom selectedfrom the group consis'tingof chlorine, bromine and .iodine atoms, the concentration of said palladium salt in the. emulsion being equal to from 0.015 to 0.2% by moles of. the silver halide in the emulsion.

2. A high speed photographic gelatino-silverhalide developing-out emulsion sensitized-with. at least .onegold compound in a concentration: equal to from 0.001. to 0.01% by moles of'the-sllyer halide in the emulsion, said emulsion containing as a supersensitizer. .at least one palladium salt selected from; the group consisting of palladium salts represented by the following general formulas:

MzPdXs and M2PdX4.

wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms, the concentration of said palladium salt.- in the emulsion being equal to from 0.015 to 0.2% by moles of'the silver halidein the emulsion.

3. A high speed. photographic gelatino silverhalide. developing-out. emulsion sensitized withat least one gold salt selected from those represented by the following. general formula:

wherein M represents an, alkali metal atom, said emulsion containing; asa supersensitizer; at least one palladium salt selected from those represented by 'the" followinggeneral formula:

M'zPdCle wherein M represents an alkali metal atom, the concentration of said .gold. salt being equal to from 0.001 to0.0l% by moles of thesilver halide in the emulsion and the concentration. of said palladium salt being equal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

4. A high speed photographic gelatinoesilverhalide developing-out emulsion sensitized with potassium chloroaurate (KAuCl-r) in a. concentration equal to from 0.001 to 0.01% by moles'of the silver halide in the emulsion, said emulsion containing, as a supersensitizer, potassium chloropalladate (KiPdCle) in a concentrationequal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

5. Ahigh speed photographic gelatino-silverhalide developing out emulsion sensitizedv with potassium chloroaurate (KAuCh) in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion, said emulsion containing, as a-supersensitizer, potassium chloropalladite" (K2PC1C14) in a concentration equal to from 0.015 to 0.2% by moles of the-silver-halide in the emulsion.

6. A high speed photographic gelatinorsilverhalide developing-out emulsion sensitized with potassium chloroaurate (KAuCh) in. aconcentration equal to from 0'.001.to 0.01% bymoleszof salts represented by the following general formulas MzPdXs and MzPdXa wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms, the concentration of said palladium salt in the emulsion being equal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

8. A high speed photographic gelatino-silverhalide developing-out emulsion sensitized with at least one gold compound in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion, and at least one thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates in a concentration equal to from 0.1 to 2.5% by moles of the silver halide in the emulsion, said emulsion containing, as a superseneitizer, at least one palladium salt selected from the group consisting of palladium salts represented by the following general formulas:

MIzPdXs and M2PdX/l wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms, the concentration of said palladium salt in the emulsion being equal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

9. A high speed photographic gelatino-silverhalide developing-out emulsion sensitized with at least one gold salt selected from those represented by the following general formula:

M'AuCh wherein M represents an alkali metal atom, in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion, and at least one thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates in a concentration equal to from 0.1 to 2.5% by moles of the silver halide in the emulsion, said emulsion containing, as a supersensitizer, at least one palladium salt selected from those represented by the following general formula:

MzPdCls wherein M represents an alkali metal atom, the concentration of said palladium salt in the emulsion being equal to from 0.03 to 0.15%

- by moles of the silver halide in the emulsion.

10. A high speed photographic gelatino-silverhalide developing-out emulsion sensitized with potassium chloroaurate (KAuCh) in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion, and at least one thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates in a concentration equal to from 0.1 to 2.5% by moles of the silver halide in the emulsion, said emulsion containing, as a supersensitizer, potassium chloropalladate -(K2PdCl6) in a concentration equal to from 0.03 to 0.15% by moles of the silver halide in the emulsion.

11. A high speed photographic gelatino-silverhalide developing-out emulsion sensitized with potassium chloroaurate (KAuCh) in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion, and at least one thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates in a concentration equal to from 0.1 to 2.5% by moles of the silver halide in the emulsion, said emulsion containing, as a supersensitizer, potassium chloropalladite (KzPdCh) in a concentration equal to from 0.03 to 0.15% by moles of the silver halide in the emulsion.

12. A high speed photographic gelatino-silverhalide developing-out emulsion sensitized with potassium chloroaurate (KAuCh) in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion, and at least one thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates in a concentration equal to from 0.1 to 2.5% by moles of the silver halide in the emulsion, said emulsion containing, as a supersensitizer, potassium bromopalladate (KzPdBrs) in a concentration equal to from 0.03 to 0.15% by moles of the silver halide in the emulsion.

13. A process for preparing a high speed photographic silver halide emulsion comprising sensitizing the emulsion with at least one gold compound in a concentration equal to from 0.0003 to 0.015% by moles of the silver halide in the emulsion and adding to the sensitized emulsion at least one palladium salt selected from the group consisting of palladium salts represented by the following general formula:

IMzPdXs and M2PdX4 wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms, the con centration of said palladium salt in the emulsion being equal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

14. A process for preparing a high speed photographic silver halide emulsion comprising sensitizing the emulsion with at least one gold compound in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion and at least one sulfur sensitizer. and adding to the sensitized emulsion at least one palladium salt selected from the group consisting of palladium salts represented by the following general formulas:

MzPdXe and M2PdX4 wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms, the concentration of said palladium salt in the emulsion being equal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

15. A process for preparing a high speed photographic silver halide emulsion comprising sensitizing the emulsion by digesting it on the acid side of neutrality in the presence of at least one gold compound in a concentration equal to from 0.001 to 0.01% by moles of the silver halide in the emulsion and at least one sulfur sensitizer, and adding to the sensitized emulsion at least one palladium salt selected from the group consisting of palladium salts represented by the following general formulas:

MzPdXs and lVI2PdX4 wherein M represents a member selected from the group consisting of an alkali metal atom and an ammonium radical, and X represents a halogen atom selected from the group consisting of chlorine, bromine and iodine atoms, the con- 10 centration of said palladium salt in the emulsion being equal to from 0.015 to 0.2% by moles of the silver halide in the emulsion.

ROBERT E. STAUFFEER.

5 WILLIAM F. SMITH.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name Date 2,059,642 Kankelwitz Nov. 3, 1936 2,399,083 Waller et al Apr. 23, 1946 15 2,448,060 Smith et a1 Aug. 31,1948 2,540,086 Baldsiefen et al. Feb. 6, 1951

Claims

1. A HIGH SPEED PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIZED WITH AT LEAST ONE GOLD COMPOUND IN A CONCENTRATION EQUAL TO FROM 0.0003 TO 0.015% BY MOLES OF THE SILVER HALIDE IN THE EMULSION, SAID EMULSION CONTAINING AS A SUPERSENSITIZER, AT LEAST ONE PALLADIUM SALT SELECTED FROM THE GROUP CONSISTING OF PALLADIUM SALTS REPRESENTED BY THE FOLLOWING GENERAL FORMULAS: