US2271623A

US2271623A - Photographic emulsion

Info

Publication number: US2271623A
Application number: US321595A
Authority: US
Inventors: Burt H Carroll
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1939-03-30
Filing date: 1940-02-29
Publication date: 1942-02-03
Anticipated expiration: 1959-02-03
Also published as: FR949227A; GB527296A; BE466375A

Description

Feb. 3, 1942. CARROLL 2,271,623

PHOTOGRAPHIC EMULSION Filegi Feb. 29, 1940 DENSITY g WAVELENGTH (mp) BURT .H. CARROLL INVENTOR Byyg ATTOR YS Patented Feb. 3, 1942 am 11. Carroll, Rochester, 1v. 2., to"

Eastman Kodak Company, Rochester, -N.' -Y.,'a'.

corporationoi'hlcwJcrseyv Application February 29, 1940, Serial uni-ears In Great Britain March 30, 1939 19 Claims. 95-71) This invention relates to photographic emulsions and more particularly to photographic emulsions of the silver halide type.

It is known that the inherent sensitivity of photographic silver halide emulsions (whether spectrally sensitized or not) can be enhanced, and there has been a constant eifort to, produce higher speeds in photographic emulsions. For example, it is known that the speed of'gelatinosilver-halide emulsions'can be enhanced by an extended digestion or ripening of the emulsion.

It is also known that the speed of silver halide emulsions (spectrally sensitized or not) can bev enhanced by incorporating in the emulsions compounds containing a divalent atom of the sulfur group directly joined by a double bond to a single metalloid atom to which is attached at least another group of atoms. Examples of such compounds are allyl isotliiocyanate andallylthiourea.

I have now found that the speed of photographic silver halide emulsions can be increased by incorporating in the emulsions (spectrally sensitized or not) surface active substances, such as aqueous dispersing or wetting agents for example, of the cationic ammonium salt type. (Surface active substances are classified as anionic and cationic or non-ionic, depending upon whether or not the substances ionize, and if so, depending upon whether the anion or the cation is surface active. Surface active materials are sometimes referred to as capillary active materials, lipophyle materials or materials which possess interface modifying properties.)

My new method of sensitizing emulsions is an improvement over the known methods of enhancing sensitivity, since the speed increases attained by my new method are complementary to the speed increases that can be attained by the prior methods.

The surface-active substances act on the emulsion in unknown manner to increase its effective sensitivity. As a result, the sensitivity is increased by about the same amount at any wavelength within the range of its spectral sensitivity, although in spectrally sensitized emulsions there is frequently observed an appreciable increase in relative sensitivity for longer wavelengths. Inasmuch as the silver ion and hydrogen ion concentration in my emulsions appear to undergo little or no change by virtue of the presence of the surface active substances, I shall refer to the action of the surface active substance as a kind of supersensitization, and I shall refer to mixtures of the surface active substances and spectral (optical) sensitizers as combinations, although I do not intend to imply that the surface active substance and the spectral sensitizer are chemically combined.

My new supersensitized emulsions are an improvement over emulsions known:

in the art. The increases in sensitivity which can be attained with supersensitiz'ingcombinations of dyes can be enhanced by my new method. Furthermore, whereas with supersensitizing combinations of sensitizing 'dyes- (see United States Patents 2,075,046, 2,075,047, and 2,075,048, each dated March 30, 1937), the supersensitizing effect is confined more or less to a single spectral region, the supersensitization attained in my new emulsions extends throughout the entire region in which the spectral sensitizer acts (and is fairly uniform in degree throughout the entire region), while at the same time the sensitivity in the violet and blue region (where the spectral sensitizer does not act) is also enhanced about to the same degree.

An object of my invention, therefore, is to provide new photographic emulsions. A further object is to provide emulsions sensitized with a.

- supersensitizing combination of a sensitizing dye and a surface active material. A further object is to provide a process for preparing such emulsions.

According to my invention, I incorporate in a photographic silver halide emulsion a cationic surface active ammonium salt substance. The surface active substance can be incorporated in any suitable form, e. g. in the form of a solution in a suitable solvent, such as water or methyl alcohol. The surface active material should b thoroughly incorporated in the emulsion. The surface active substance can be added to the finished emulsion or at any stage of the preparation of the emulsion.

In the case of spectrally sensitized emulsions, the surface "active substance can be incorporated in the emulsion before, simultaneously with, or,

after the sensitizing dye, although in some cases, as hereinafter set forth,it is advantageous to incorporate the sensitizing dye before incorporating the surface active material. The methods of incorporating sensitizing dyes in emulsions are, of course, well known to those skilled in the art. Ordinarily, it is advantageous to employ asolution of the sensitizing dye in a suitable solvent, e. g. methyl alcohol. Ethyl alcohol or "acetone may be employed in cases where the solubility of the sensitizing dye in methyl alcohol is very low.

sensitizing dyes are ordinarily incorporated in the washed finished emulsions, and in accordance with my invention, the surface active substances are advantageously also incorporated in the washed finished emulsions. However, the surface active substance canbe added to the emulsion during the preparation thereof, i. e. during the precipitation, the first digestion or the second digestion (the ripening). After preparing the emulsions in the presence of the surface active substance, the sensitizing dyes can be incorporated in the so-prepared emulsion.

As cationic ammonium salt surface active substances, I have found that those which do not contain a hydrogen atom on the ammonium nitrogen atom (i. e. the so-called quaternary ammonium types) are advantageously employed.-

As cationic quaternary ammonium salt surface active substances, I include particularly those having at least one lipophylic quaternary ammonium cation containing four separate alkyl groups (alcohol radicals) attached to the quaternary ammonium nitrogen atom, as well as those having at least one lipophylic quaternary ammonium cation in which the quaternary ammonium. nitrogen atom is one of the nuclear atoms of a heterocyclic ring (the nuclear atoms of which advantageously consist of carbon and nitrogen atoms), said ring being devoid of fusedon aromatic rings. I

I have found that the ammonium cation (quaternary or not) advantageously should contain at least one organic group containing a chain of at least eight members. Advantageously, such members are from the group consisting of carbon, oxygen, nitrogen and sulfur atoms. One

'or more aromatic rings, such as a benzene ring for example, can take the place of one or more ofthe eight or more atoms. Thus, a benzene ring can take the place of one atom, while a naphthalene ring (two benzene rings fused together) can take the place of two atoms. The atoms attached to the eight or more atoms in the chain (where valence permits) can be hydrogen, oxygen, carbon, or halogen for example. Any aromatic ring system in the chain can carry simple substituents. The organic group containing a chain of eight or more atoms can be attached directly to the ammonium nitrogen atom or indirectly thereto by means of a group of atoms. I have found that cationic ammonium salt surface active substances, especially the quaternary type, having an ammonium cation containing a lipophylic organic group which contains a chain composed of from nine to twelve members selected from the group consisting of carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms and aromatic ring systems, are advantageously employed.

The anion may be any acid radical, such as chloride, bromide, iodide, p-toluenesulfonate, perchlorate or alkylsulfate for example. Of course, introduction of halide anions into photographic silver halide emulsions alters the halide concentration in the emulsion and compensating changes in the emulsion may be necessary, if such ammonium salts are employed. For this reason, I ordinarily prefer to employ surface active substances containing anions other than halides. Perchlorates and p-toluenesulfonates are advantageously employed;

Following are representative cationic ammonium salt surface active substances especially useful in practicing my invention.

1. Tetraalkyl quaternary ammonium salts which can be represented by the following general formula:

wherein at least one of the groups R, R, R" and R' represent an organic lipophylic group containing a chain of at least eight members selected from the group consisting of carbon represented by the following general formula:

wherein R represents an organic lipophylic group containing a chain of at least eight members selected from the group consisting of carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms and aromatic ring systems and x represents an acid radical or anion.

3. Pyridihium quaternary salts which can be represented by the following general formula:

wherein R represents an alkyl group, such as methyl, ethyl, butyl or benzyl for example, one of the groups R and R" represents an organic lipophylic group containing a chain of at least eight members selected from the group consisting of carbon atoms, oxygen atoms, nitrogen atoms,

sulfur atoms and aromatic ring systems while the other of the groups R and R represents hydrogen or a low molecular weight alkyl group, such as methyl, ethyl or butyl, and x represents an acid radical or anion.

4. Piperidinium salts which can be represented by the following general formula:

nsc

R i R wherein one of the groups R and R represents an organic lipophylic group, containing a chain of at least eight members selected from the group consisting of carbon atoms, oxygen atoms, nitrogen atoms, sulfur atomsand aromatic ring systems, while the other of the R and R groups represents hydrogen or a low molecular weight alkyl group, such as methyl, ethyl, butyl or benzyl for example, and X represents an acid radical or anion. I

5. Pyrazolium quaternary salts which can be represented by the following general formula:

nc--c-cm HrC- /}nx I N wherein one of the groups R and R represents an organic lipophylic group containing a chain benzyl, and X represents an acid radical or anion.

6. Imidazolinlum quaternary salts which can be represented by the following general formula:

wherein one of the R and R groups represents an organic lipophylic group containing a chain of at least eight members selected from the group consisting of carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms and aromatic ring systems while the other of theR and R groups represents a low molecular weight alkyl group such as methyl, ethyl, butyl or benzyl and X represents an acid radical or anion.

The following are representative of organic lipophylic groups containing a chain of at least eight members selected from the group consisting of carbon atoms,-oxygen atoms, sulfur atoms and aromatic ring systems:

Octyl. GET-(C1197 Nonyl, C-H (CH2)a(nil1e atom chain) Decyl, CHr-(CHz)w-(t8ll atom chain) Cetyl, CH3(CH2)1s-(sixteen atom chain) Heptoxymethyl, CHr-(CH2)0CH2'-(Ilifl6 atom chain) Undecoxy'methyl, CHI-(CH2)mO-CHa(thirteen atom chain) Butoxyethoxyethyl, CH:(CHz)a-O(CHr)7"O-CHgCH2- (ten atom chain) 'ler-butylphenoxyethoxyethyl,

CH; (eight atom+phenyl group chain) Formylphenyloxyethoxyethyl OCHzCHz-OCHr-CH:- H (seven atom+phenyl group chain) Phenylphenoxyethoxyethyl (six atom+two phenyl groups chain) Methylphenoxypropoxypropyl cm-Qo-wmnm-wngr (nine atom-l-phenyl group chain) HOCH2(CH:) l-CHF (eleven atom chain) B-Naphthoxyethoxyethyl I have found that pyridinium quaternary salt surface active agents are especially advantageously employed. The quaternary salt surface active agents derived from dibenzymethyl and dibenzyethyl amines are also advantageously employed. These dispersing agents tend to produce lesser photographic fog.

I have found it advantageous to incorporate spectral sensitlzers in the photographic emulsions prior to incorporation of the perchlorate surface active agents in the emulsions. With surface active agents containing other anions, the order of incorporation of the agent with'respect to the spectral sensitizer appears to be of small moment.

The quantity of surface active agent which is mostv advantageously employed varies with the nature of the surface active agent and with the nature of the emulsion. Ordinarily the most advantageous concentration was found to be between about 20 mg. and about 200 mg. of the surface active agent per gram-mole of silver halide in the amulsion, although greater or smaller concentration can be employed. I have found that excesses of the surface active agent are advantageously avoided, since excesses produce fog in the emulsions. For surface active agents containing a lipophylic group containing achain of eight to ten members, I have found that as much as about 400 mg. of surface active agent per mole of silver halide in the emulsion can ordinarily be employed without encountering excessive fog, while with surface active agents containing a lipophylic group containing a chain of eleven to twelve or more members, I have found that not more than about 200 mg. of surface active agent per mole of silver halide should ordinarily be employed.

The optimum range of concentration for any particular surface active agent is ordinarily fairly narrow and can best be determined by employing a series of concentrations of the surface active agents, separately in several batches of the same emulsion and determiningthe sensitivity of the several emulsions, before and after incorporation of the surface active agent, in a conventional manner, well known to those skilled in the art. Briefly, the method of determining sensitivity of emulsions comprises coating the emulsion onto a glass plate to a suitable thickness and drying the coated emulsion, and then testing the resulting photographic plate in a wedge spectrograph and a sensitometer, whereby spectral sensitivity and speed of the emulsion on the plate is determined.

When employing spectrally sensitized emulsions, the spectral sensitizers are advantageously employed in about their optimum concentration which ordinarily lies between about 3 mg. and 20 mg. of spectral sensitizer per liter of emulsion containing about 0.25 mole of silver halide, although concentrations above or below the optimum concentration can be employed. With fine-grain emulsions (which includes most of the ordinarily employed silver chloride emulsions), the ratio of concentration of sensitizing dye to the concentration of silver halide in the emulsion is advantageously larger than in the coarser grain emulsion, where smaller amounts of sensitizing dye usually give optimum sensitization. The optimum concentration, as above referred to, of a sensitizing dye (i. e. the concentration at which greatest sensitivity occurs) can be readily determined in a mannerwell known to those skilled in the art by measuring the sen- My invention is directed particularly to the silver-halide developing-out emulsions customarily employed in the art, including the gelatino- A silverchloride, the gelatino-silver-bromide and the gelatino-silverbromiodide developing-out emulsicns, for example. However, my invention can be employed with silver halide emulsions wherein the carrier is other than gelatin, for example a resinous or cellulosic substance which has substantially no deleterious eifect on the light-sensitive materials in the emulsions.

As spectral sensitizers (sensitizing dyes), only those which are non-acidic can be employed in practicing my invention. sensitizing dyes, such as Congo red, which disperse in water to give a colored anion, i. e. acidic sensitizing dyes, appear to interfere with the surface active agent, with the result that neither the acid dye nor the surface active substance exert a. substantially beneficial effect on the emulsion. As non-acidic sensitizing dyes, I include all the known neutral and basic sensitizing dyes, i. e. those sensitizing dyes which do not give colored anions. Some of these non-acidic sensitizing dyes, such as the cyanine dyes, give colored cations. Exemplary of the non-acidic sensitizing dyes are the sensitizing cyanine dyes (see, for example United States Patents 1,846,300; 1,846,301; 1,846,302; 1,846,303 and 1,846,304 each dated February 23, 1932, United States Patent 1,861,836, dated June 7, 1932, United States Patent 1,939,201, dated December 12, 1933, United States Patent 1,942,- 854, dated January 9, 1934, United States Patent 1,957,869, dated May 8, 1934, United States Patent 1,962,124, dated June 12, 1934, United States Patent 1,969,446, dated August 7, 1934, United States Patent 1,973,462, dated September 11, 1934; United States Patent 1,990,507, dated February 12, 1935, United States Patent 2,094,580, dated October 5, 1937, United States Patent 2,112,140, dated March 22, 1938 and French Patent 757,813, published January 5, 1934), the sensitizing merocyanine dyes (see United States Patent 2,078,233, dated April 27, 1937, United States Patent 2,089,729, dated August 10, 1937, United States Patent 2,153,169, dated April 4, 1939 and United States Patents 2,177,401; 2,177,-

sensitizing hemicyanine dyes (see United States Patent 2,166,736, dated July 18, 1939) and the sensitizing hemioxonol dyes (see United States Patent 2,165,339, dated July 11, 1939 and French Patent 841,632, published May 24, 1939) While the process of my invention is subject to variation particularly as respects the nature and quantity of aqueous dispersing and or wetting agent employed, the nature and quantity of the spectral sensitizer employed, if any, the nature of the silver halide emulsion employed and the manner of incorporating the dispersing agent and spectral sensitizer (if any) in the emulsions, the following example will serve to illustrate the manner of obtaining my new emulsions. This example is not intended to limit my invention.

Example Into one liter of a flowable finished washed gelatino-silver-bromiodide emulsion containing about 0.32 mole oi silver bromide, were incorporated, slowly with stirring, a concentrated methyl alcoholic solution of 2,2'-diethyl-8 methyl-3,4,3',4'-dibenzothiacarbocyanine chloride. Sufilcient of the alcoholic solution was added to incorporate about15 mg. of the carbocyanine chloride in the emulsion.

To the resulting mixture were added, slowly and with stirring, a 1% (by weight) aqueous solution of lauryltriethylammonium perchlorate. Sufllcient of the aqueous solution was added to incorporate about mg. of the perchlorate in the emulsion.

Photographic elements can be made from emulsions prepared in the above manner by coating the emulsions to a suitable thickness on a suitable support and drying the coated emulsion, in a manner well known to those skilled in the art. Suitable supports are, of course, glass, photographic paper support and photographic film support. The photographic film support may, of course, be of cellulose acetate, cellulose nitrate or any other suitable cellulose derivative, or be of any suitable resinous material, such as a polyvinyl acetal resinous material for example. My new emulsions are advantageously coated on glass support.

The following table contains a summary of some of the more practical results I have ob- 402 and 2,177,403, dated October 24, 1939), the 50 tained by my invention.

Table White light Emulsion sensitizing dye Surface active agent Fog Speed Gamma Mg. per liter ofemulaion Mg. per liter of emulsion Gelatino-silver-bromiodide (about 2, 2'-diethyl-8metliyl-3, 4, 3, 4'-di- None 1.050 1.53 0.08

0.32 mole of silver halide per liter). benfi ihiacarbocyanine chloride, 15 (clear) mg. 1 er. Do ..do Lauryltriethyl-ammonium perchlo- 1,320 1.72 0.10

rate, 50 rug/liter. (clear) Do 2, 2-diethyl-8-methylthiacarbocya- None .4 1,260 1. 47 0.06

nine bromide, 15 mg./liter. (cl ar) Do do Lauryltriethyl-ammoniurn perchlo- 1.700 1.56 0.11

rate, 50 mgJliter. (clear) Do 3-ethyl-5-(2-ethylbenzoxazolyidene- None 775 1.01 0.06

ethylidene)-rhodanine, l0 mgJIiter. (clear) Do .do Lauryltriethyl-ammonium perchlo- 1,070 1.53 0.08

rate, 50 mg./1iter. Do 2-diphenylarnino-5-(2-ethyl-l-benzo- None 1. 510 1.50 0.08

thiazylidene-ethylidene)-4-(5)-thia- (clear) zolone, l5 mgJliter. Do o N-heptoxymethyl pyridiniuni pcr- 1.100 1.37 0.08

chlorate, 30 lug/liter. (clear) Do 2-[4-(l-piperidyl-A ,=-butadienyl)]-fl- None .1 890 0.94 0. 03

ingphthathiazole ethiodide, 50 mg./ (clear) 1 er. Do -do N-heptoxymethyl pyridiniurn per- 1.100 0.92 0.08

chlorate, 30 mg./liter. (clear) Do 3-ethyl-5-[ -(l-pipcridyl) a1lylidene1- None 630 1. 33 0.10

rhodanine, 15 mg.lliter. (clear) Do None N-heptoxymethyl-pyridinium per- 930 1.27 0.10

chlorate. (clear) (White light minus White light blue) No. 12 Emulsion sensitizing dye Surface active agent Fog filter Speed Gamma Speed Gamma Gelatino-silver-bromiodlde 2,2-di1nethyI-S-ethyl-thie- None 935 0.00 .03 265 1.1

(0.26 mole silver halide per iigrbotiyiizgline br m $3.1 "00F. Nggyl n yridinium perchlorate, 1,200 0.91 .10 330 0,00

"""" mg. i or.

Nonyl pyridinium perchlorate, 1,200 0.96 .10 445 0.86

50 trig/liter. 4 Decyl pyridinium perchlorate, 1,230 1.02 .10 390 1.08 30 mg./liter. a-nonyl-N-methyl pyridinium 1,200 0.94 .08 425 0.99

rchlorate 20 mg./l1ter. pert. butyl phenoxy-ethoxy- 1,380 0.84 .09 305 0.87

ethyl p ridinium perchlorate 30 mg./l ter. N-nonyl piperidinium methyl 1,000 0.97 .10 295 1.00

istioluene sulionate, 30 mg./

r. Hexoxymethyl pyridinium per- 1,100 0.95 .10 325 1.03.

chlorate, 50 mg./l1 ter. Hegtoxymethyl pyr dinium per- 1, 120 0. 97 11 390 0.99

c lorate, 50 mg./l1ter. Octoxymethyl pyridinium per- 1,230 1.05 .11 525 1.00

chlorate 30 mg./liter. Nonoxyethyl pyridinium per- 1,750 0.98 16 630 1.05

chlorate, 30 mg./liter. N-decyl-l,3 o-trimethyl pyrazo- 1, 350 0. 99 .10 465 0. 94

lium perchlorate 30 rug/liter. N-Carbomonoxymethyl pyri- 1,180 0.92 .09 455 0.94

iiitgium perchlorate, 30 mg./

1 r. 1 none e NODB 720 1.08 .05 Do $1 132) Heptoxymethylpyridinium per- 870 1.07 .05

chlorate, 20 mg./liter. Heptoxymethylpyridinium per- 950 1. 04 05 chlorate 30 mg./liter. Do Ethylene his dioxymcthyl pyri- 930 1. .06

""""""""""""" iiiigium perchlorate, mg./

r. Ethylene bis dioxymethylpyril 100 1.06 .06 Do ditrgium perchlorate, mg./

r. n-Nonyl pyridinium perchlo- 1 000 1.03 .05 Do rate, 30 mg./liter. Do do ay -N-methyl pyridinium 1,100 1.03 .05

""""""""""" perchlorate, 15 mg./liter.

The improvement produced by my invention may still be more readily appreciated from an inspection of a graphic representation.

The accompanying drawing is a reproduction of two spectral sensitivity curves. Curve A represents the spectral sensitivity of a gelatino silver bromiodide emulsion (about 0.25 mole of silver halide per liter of emulsion) containing sensitizing dyes such as thiacarbocyanine dyes and 2'-cyanine dyes as described in Mees U. S. Patent 2,158,882, granted May 16, 1939.

Curve B represents the spectral sensitivity of the same dyed emulsion but containing in addition a cationic surface active salt in accordance with the present invention in the concentration of approximately 15 mg. per liter of emulsion.

The spectral sensitivity curves were determined as described by Jones and Sandvik in the Jour. of the Optical Soc. of America, vol. 12, page 401,

It will be seen from a consideration of these curves that not only is the spectral sensitivity of curve B an improvement over curve A, but this improvement extends over the entire curve and more or less the same degree of improvement. It is in these latter features that my invention constitutes a rather marked departure from the prior art.

It will be observed that in the tables I have described a. number of examples of perchlorate derivatives, inasmuch as this particular derivative is preferred, because of the improved properties thereof. However, it is also to be observed that the p-toluene-sulfonates and other derivatives such as bromides and the like are also satisfactory in the practicing of my invention.

These derivatives may be produced by a variety of methods and obtained from any source assuming, of course, that the materials meet photographic specifications.

However, I prefer to obtain perchlorate derivatives by the novel method described in Allen and Wilson application, filed of even date, entitled Surface active materials."

The sulfonates, bromides and other derivatives may be satisfactorily produced by known methods; hence, reference to a description thereof is unnecessary.

It is apparent from the foregoing that my invention is susceptible of some modification; hence, I do not wish to be restricted excepting insofar as may be necessitated by the prior art and the spirit of the appended claims.

What I claim as my invention and desire to be secured by Letters Patent of the United States'is:

1. A photographic silver halide emulsion sensitized with a cationic surface active ammonium salt.

2. A photographic silver halide developing-out emulsion sensitized with a cationic surface active ammonium salt.

3. A photographic gelatino-silver-halide emulsion sensitized with a cationic surface active ammonium salt.

4. A photographic gelatino-silver-halide developing-out emulsion sensitized with a cationic surface active ammonium salt.

x 5. -A photographic gelatino-silver-halide emulsion sensitized with a supersensitizing combination of at least one non-acidic sensitizing dye together with a cationic surface active ammonium salt.

6. A photographic Silver halide emulsion sensitized with a cationic surface active quaternary emulsion sensitized with a cationic surface active quaternary ammonium salt.

8. A photographic gelatino-silver-halide emulsion sensitized with a cationic surface active quaternary ammonium salt.

9. A photographic gelatino-silver-halide developing-out emulsion sensitized with a cationic surface active quaternary ammonium salt.

10. A photographic silver halide emulsion sensitized with a supersensitizing combination of at least one non-acidic sensitizing dye together with a cationic surface active quaternary ammonium salt.

11. A photographic gelatino-silver-halide emulsion sensitized with a supersensitizing combination of at least one non-acidic sensitizing dye together with a cationic surface active quaternary ammonium salt.

12. A photographic gelatino-silver-halide emulsion sensitized with a supersensitizing combination of at least one non-acidic sensitizing dye together with a cationic surface active tetra-alkyl quaternary ammonium salt.

13. A photographic gelatino-silver-halide emulsion sensitized with a supersensitizing combination of at least one non-acidic sensitizing dye together with a cationic surface active pyridinium alkyl quaternary salt.

14. A photographic gelatino-silver-halide emulsion sensitized with a supersensitizing combination of at least one non-acidic sensitizing dye together with a cationic surface active N-alkylpiperidinium quaternary salt.

15. A photographic gelatino-silver-halide emul-' sion sensitized with a supersensitizing combination of a non-acidic sensitizing dye together with a cationic surface active quaternary ammonium salt, the cation of which contains at least one organic group containing a chain of at least eight members selected from the group consisting of carbon atoms, oxygen atoms. sulfur atoms, nitrogen atoms and benzene nuclei.

16. A photographic gelatino-silver-halide emulsion sensitized with a supersensitizing combination of a non-acidic sensitizing dye together with a cationic surfaceactive quaternary ammonium, salt, the cation of which contains at least one organic group containing a chain of from nine to twelve members selected from the group consisting of carbon atoms, sulfur atoms, oxygen atoms, nitrogen atoms and benzene nuclei.

17. A photographic gelatino-silver-halide emulsion sensitized with at least one non-acidic sensitizing dye and containing, in a concentration of from about 20 to about 400 milligrams per grammole of silver halide in the emulsion, a cationic surface active quaternary ammonium salt, the cation of which contains at least one organic group containing a chain of from 9 to 10 members selected from the group consisting of carbon atoms, sulfur atoms, oxygen atoms, nitrogen atoms and benzene nuclei.

18. A photographic gelatino'silver-halide emulsion sensitized with at least one non-acidic sensitizing dye and containing, in a concentration of from about 20 to about 200 milligrams per grammole of silver halide in the emulsion, a cationic surface active quaternary ammonium salt, the cation of which contains at least one organic group containing a chain of from 11 to 12 members selected from the group consisting of carbon atoms, sulfur atoms, oxygen atoms, nitrogen atoms and benzene nuclei.

19. An undyed gelatino silver halide emulsion containing, at least, one cationic surface active ammoniuma salt in a concentration equal to less than 400 milligrams per gram-mole of silver halide in the emulsion.

BURT H. CARROLL.