US2334864A - Photographic emulsion - Google Patents

Description

PHOTO GRAPHIC EMULSION Burt H. Carroll and John Spence, Rochester, N. Y.,

assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application February 2, 1942, Serial No. 429,282

14 Claims.

This invention relates to photographic emulsions and more particularly to sensitized photographic emulsions.

It is known that the sensitivity of photographic silver halide emulsions, whether spectrally sensitized or not, can be increased by incorporating in the emulsions cationic surface-active quaternary ammonium salts. (See the copending application of Burt H. Carroll, Serial No. 321,595, filed February 29, 1940, now Patent No. 2,271,623 of February 3, 1942.) The effect of these cationic surface-active ammonium salts i generally independent of spectral (optical) sensitization and involves no appreciable change in distribution of spectral sensitivity. These cationic surface-active materials are effective in low concentrations, i. e., concentrations of the order of to 200 mg. per gram-mole of silver halide in the emulsion. (It is to be understood that the term surfaceactive is used throughout this specification and the claims in the usually accepted manner, viz, to refer to activity at liquid-air interfaces and not to activity at interfaces, such as the liquid silver halide interfacces of a photographic emulsion) It is further known that the sensitivity of photographic silver halide emulsions, whether spectrally sensitized or not, can be increased by incorporating in the emulsions polyammonium salts to another quaternary ammonium salt group. linked by at least one bivalent organic radical to another quaternary ammonium salt group. (See the copending application of Burt H. Carroll and Charles F. H. Allen, Serial No. 321,594, filed February 29, 1940, now Patent No. 2,288,226 of June 30, 1942.) These polyammonium salts need not be surface-active, and their effect (as in the foregoing case) is generally independent of spectral sensitization and involves no appreciable change in the distribution of spectral sensltivity. These polyammonium salts are also effective in low concentrations. Moreover, these polyammonium quaternary salts have an advantage over the aforesaid cationic surface active ammonium salts, in that the polyammonium quaternary salts show little or no tendency to diffuse from the emulsions into the film support upon which the emulsions are coated.

We have now found that certain substantially non-surface active, substantially colorless cyclammonium quaternary salts and certain substantially non-surface active, substantially colorless non-quaternary cyclammonium salts sensitize photographic emulsions. Moreover, these cyclammonium salts increase sensitivity in a manner different from that of the aforesaid surface-activ quaternary ammonium salts, in that the instant salts frequently alter the distribution of spectral sensitivity of spectrally sensitized emulsions. Moreover, the instant salts must ordinarily be employed in much larger concentrations than the aforesaid surface active salts in order to secure maximum eiiects. Furthermore, little or no trouble is encountered, owing to diffusion of the instant cyclammonium salts from the emulsions into the film support. (By substantially non-surface active we mean no more surface activity than of the order of that encountered with such cyclammonium salts as pyridine c-phenylethyl bromide or a-picoline 'y-phenyl-n-propyl bromide.)

Our invention is not to be confused with prior proposals to employ cyclammonium quaternary salts in photographic emulsions to combine with acid dyes in order to prevent diffusion of the dyes. In the presence of sufiicient acid dyes (even acid sensitizing dyes) to combine with our cyclammonium salts, the salts do not have a desirable effect. In our new emulsions, any acid dye in the emulsion must be present in a concentration low enough that a sufficient amount of the cyclammonium salt to sensitize the emulsion is uncombined with the acid dye.

It is accordingly an object of our invention to provide new photographic emulsions. A further object is to provide a process for preparing such emulsions. Still other objects will appear hereinafter.

In accordance with our invention, we incorporate substantially non-surface active, substantially colorless cyclammonium salts in a photographic silver halide emulsion, such as a silver bromide emulsion, a silver chlorobromide emulsion or a silver bromiodide emulsion. The eyelammonium salts which we employ have no action on silver chloride emulsions, and silver chloride emulsions are not within the purview of our invention.

As cyclammonium salts, we employ cyclammonium quaternary (with no hydrogen atoms on the cyclammonium nitrogen atom) salts, as well as non-quaternary cyclammonium salts in which there is one hydrogen atom on the cyclammonium nitrogen atom and but two of the remaining valences of the cyclammonium nitro atom are employed in the formation of a cyclic nucleus. Pyridine quaternary salts, such as pphenylethyl pyridinium bromide:

CeIh-CHr-CH: Br

exemplify the quaternary type, and N-alkylpiperidine salts, such as N-(fi-phenylethyl)-piperidine bromide:

exemplify the non-quaternary type.

Whether quaternary or not, the cyclammonium salts which we employ are substantially non-surface active and substantially colorless and contain not more than one quaternary nitrogen atom and contain only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom and contain no quaternary nitrogen atom linked by a conjugated carbon chain to a ternary nitrogen atom.

The most effective cyclammonium quaternary salts appear to be (1) those in which the quaternary nitrogen atom is the nitrogen atom of a pyridine nucleus, such as pyridine quaternary salts, quinoline quaternary salts, isoquinoline quaternary salts and benzoquinoline quaternary salts, (2) those in which the quaternary nitrogen atom is the nitrogen atom of a reduced pyridine nucleus, such as quaternary salts derived from N-alkyl piperidines and (3) those in which the quaternary nitrogen atom is the nitrogen atom of a benzimidazole or indazole nucleus. Some effects have been obtained with fi-naphthothiazole quaternary salts, and benzothiazole quaternary salts definitely alter the distribution of spectral sensitivity of optically sensitized emulsions without, however, increasing the general sensitivity. However, these sulfur-containing compounds are not within the purview of our invention.

Advantageously the cyclammonium salts employed are aralkyl cyclammonium salts, especially good efiects having been obtained with sphenylethyl and v-phenylpropyl salts. The nature of the acid radical of the cylammonium salt is of small import, except that iodides should not be employed in high concentrations.

The cyclammonium salts may carry substituents, e. g. alkyl, alkoxyl, arylmercapto, carboxylalkyl, halogen, carboxyl or thioalkyl. However, nitro, sulfonic acid or sulfonate groups should be avoided, since such derivatives usually do not exert a desirable effect.

The effect of our cyclammonium salts is less dependent upon conditions of development than is the case with the cationic surface active ammonium salts or the polyammonium quaternary salts referred to above. The efiect, however, varies appreciably with the type of emulsion. It has been observed that in silver bromiodide emulsions made with ammoniacal silver oxide, the change in distribution of spectral sensitivity is not great, although the increase in total (white light) sensitivity is of the same order as in the case of emulsions made with silver nitrate. The

same is true of chlorobromide emulsions. In such emulsions, cyclammonium bromides or iodides are undesirable and are advantageously replaced by chlorides or perchlorates.

The cyclammonium salts are advantageously incorporated in the emulsions in the form of aqueous or methyl alcoholic solutions. The salts should be thoroughly distributed throughout the emulsion. The quantity of cyclammonium salt which gives th maximum effect will, of course, vary with the nature of the salt and the type of emulsion. Ordinarily this quantity lies between about 0.2 gram to about 4 grams of cyclammonium salt per gram-mole of silver halide in the emulsion. ,The optimum concentration for any particular salt can readily be determined by examining the effect of a series of difierent concentrations.

In the case of spectrally sensitized emulsions, the cyclammonium salt can be incorporated in the emulsion before, simultaneously with or after the sensitizing dye, except in the case of cyclammonium perchlorates, when the cyclammonium salt is advantageously incorporated in the emulsion after the sensitizing dye.

The methods of incorporating sensitizing dyes in emulsions are, of course, well known to those skilled in the art. Ordinarily, the dyes are advantageously incorporated in the emulsions in the form of methyl alcoholic solutions. Acetone or ethyl alcohol may be employed where the solubility of the sensitizing dye is low in methyl alcohol. The sensitizing dye can be employed in any desired concentration. Frequently the optimum concentration (at which greatest sensitivity is conferred) of a sensitizing dye is within the range, 10 mg. to 30 mg. of dye per liter of emulsion containing about 0.25 gram-mole of silver halide.

Our cyclammonium salts ordinarily depress the sensitivity conferred upon emulsions by acid sensitizing dyes, i. e., sensitizing dyes containing sulfonic, sulfinic or carboxylic acid groups or the like or the salt forms of such groups. Thus, the

sensitization produced by erythrosin is considerably depressed by the quaternary salts.

In emulsions spectrally sensitized with many cyanine dyes, a change in the distribution of spectral sensitivity is obtained and this change always takes the form of an increase in relative sensitivity for the longer wavelengths. The changes in distribution of spectral sensitivity may occur even though a supersensitizing combination of sensitizing dyes is involved. For example, the combinations of 3,3'-diethyl-9-methylthiacarbocyanines with 2'-cyanines (see United States Patent No. 2,158,882, dated May 16, 1939) can be further supersensitized by means of our cyclammonium quaternary salts.

In emulsions spectrally sensitized with merocyanine dyes, no change in the distribution of spectral sensitivity is usually obtained, although useful increases in the general sensitivity are obtained. Even in a few cases where the relative spectral sensitivity is reduced, a useful increase in general sensitivity is obtained.

The cyclammonium salts interfere with the sensitization of certain cyanine dyes. With the diand tri-carbocyanines, there is little evidence of any supersensitizing effect on the dyes, and in certain cases there is actual interference with optical sensitization. Results with dibenzothiacarbocyanines are not entirely satisfactory.

In general, the greatest two-fold response (change of distribution of spectral sensitivity and increase of general sensitivity) is obtained with emulsions spectrally sensitized with the oxacarbocyanines, oxathiacarbocyanines, oxaselenacarbocyanines, thiacarbocyanines, selenathiacarbocyanines and selenacarbocyanines.

To prepare an emulsion sensitized in accordance with our invention, the following procedure is satisfactory: Into one liter of a flowable gelat-v ino-silver-halide emulsion containing about 0.23 gram-mole of silver halide was added, with stirring, a methyl alcoholic solution of a sensitizing dye. The dye was thoroughly dispersed throughout the emulsion. To the resulting sensitized emulsion was then added, with stirring, an aqueous solution of one of our cyclammonium salts, The salt was thoroughly dispsersed throughout the emulsion. The resulting emulsion can then be coated, dried and exposed in the usual manner. Our cyclammonium salts are advantageously added to the washed, finished emulsions.

The following table contains data. which illustrate the useful effects obtainable in accordance with our invention.

TABLE 4 N-p-phenylethylpyridinium bromide N-ethyl 4 phenylmercapto pyridinium iodide N- s-phenylethyl-a-picolinium bromide--- N- y-phenyl-n propyl-a-picolinium bromide N-p-phenylethyl-a-picolinium iodide- N-fi-phenylethyl-fl-picolinium bromide N-B-phenylethyl y-picolinium bromide N-ethyl-G-m'ethyl quinolinium iodide N-ethyl 6 methoxy quinolinium bromide N-p-phenylethyl quinolinium bromide N-ethyl quinaldinium bromide N-p-hydroxyethyl lepidinium perchlo- N-B-acetoxyethyl lepidinium perchlorate N-benzyl pyridinium bromide N-cinnamyl pyridinium perchlorate N-p-chlorobenzyl pyridinium perchlorate- N-cinnamyl-a-picolinium perchlorate- TABLE 1 Fast gelatino-silver-bromiodide emulsion containing about 0.23 gram-mole of silver halide per re and s i d with 20 mg. p liter -diethyl 9 methyl-selenacarbocyam'ne bromide Clem. exp Blue No. 47 filter Green No. 58 filter Red No. filter Cyclammonium quaternary salt exp exp. Fog

Speed Gamma Speed Gamma Speed Gamma Speed Gamma None 1,150 1.30 225 1.14 170 1.30 93. 5 1. 4a .11 a-Plcolme 1, 400 1.11 235 1.15 200 1. 32 140 1. as 12 B-Phenylethyl bromide:

3:32iiillfiitiIII:3:31:::::::::::::::::::"'::'"::} 300 115 265 'y-Phcnyl-mercaptmpyridine ethiodide, 0.125 g./l r 1, 500 1. 50 255 0.92 155 l. 08 370 1. l5 11 2-methyl quinoline methiodide, 0,05 g./llter 1, 350 1. 26 265 l. 12 265 l. 29 148 1. 38 l0 2-methoxy quinolino ethobromide, 0.125 g./liter 1, 550 1. 14 355 0. 92 155 1. 26 315 1.30 16 TABLE 2 N-fi-phenylethyl-3-carbethoxy pyridinium bromide Fast gelatino-szlver-bromzodide emulsion contaming about 0.23 gram-mole of silver halide per Zig br ter, sensitized with 20 milligrams of 3,1'-dieth- Nfis'p p ifiw d bmmlde :l/l-6'-methoxythia-2'-cyanine iodide N'benzyla'pmo N-p-hydroxyethyl quinaldinium perchlo- M bl N 12 an: r mt? mus gg 6 N -,B-phenoxyethyl quinaldinium perchlo- Cyclammonium quaternary salt rate Speed I Gamma Fog N-benzyl lepidinium perchlorate N -phenacyl lepidinium perchlorate None 1 162 1.21 .06 N-o-chlorobenzyl pyridinium bromide in i$niilfifi i5lildjdliBET lfii ""553 """1? i6 y l -pheny1 py p-toluene sulfonate N-benzyl quinaldinium bromide TABLE 3 N-methyl-N-'y-phenylpropyl piperidinium Fast geZatino-silver-bromiodide emulsion containr m de ing about 0.23 gram-mole of silver per liter and N-fi-phenylethyl lepidin um brom1de no spectral senstiieers N-p-chlorophenyl pyridinium bromide N -methyl-a-picolinium iodide Clear (white light) exposure cyclammonium quaternary salt Speed Gamma Fog None 1,020 1.91 .12 -Picoline g-Phenylethyl bromide, 0.125 g./liter 1, 550 1.82 .12

The following table represents the relative effectiveness of several cyclammonium salts. The greater the number of plus signs the greater the efiicacy.

sul-

N-p-phenylethyl piperidinium bromide- N-methyl-N-p-phenylethyl piperidinium cyclammonium quaternary salts which we employ can be prepared by heating heterocyclic nitrogen bases with esters (alkyl salts), e. g., alkyl halides or alkyl-p toluenesulfonates. Ordinarily an excess of the alkyl salt is advantageously employed. To obtain quaternary salts, such as the perchlorates, an aqueous solution of a quaternary halide or p-toluenesulfonate can be treated with an aqueous solution of a soluble perchlorate, e. g., sodium perchlorate. Hydroxyalkyl quaternary salts are described in United States Patent 2,213,238, dated September 3, 1940. Substituted alkyl quaternary salts are described in United, States Patent 2,231,658, dated February 11, 1941. Benzyl, p-phenylethyl and 'Y- henylpropy1 quaternary salts are described in United States Patent 2,233,511, dated March 4, 1941. Alkylmercaptoand arylmercapto-substituted quaternary salts are described in United States Patent 2,231,- 657, dated February 11, 1941, and in United States Patent 2,117,936, dated May 17, 1938. N-phenyl pyridinium chloride can be prepared according to the process described by Zincke in Ann. 333, 329. N-phenyl pyridinium bromide can be pre pared from the chloride by treating a concentrated aqueous solution of the chloride with an aqueous solution of potassium bromide.

Emulsions sensitized with the following dyes have been found to undergo especially useful changes in the distribution of spectral sensitivity with our cyclammonium quaternary salts.

3,3'-dialkyl-9-alkylthiacarbocyanine salts having the general formula:

wherein R, R and R" each represents an alkyl group and X represents an acid radical, especially those dyes wherein R, R and R" each represent an alkyl group of the formula CnH2n+1 wherein n represents a positive integer of from 1 to 2, e. g. 3,3-diethy1-9-methy1thiacarbocyanine bromide; 3,3-dimethyl-9-ethylthiacarbocyanine bromide; 3,3',9 triethylthiacarbocyanine bromide; 5,5-dichloro-3,3',9-triethylthiacarbocyanine bromide and 5-chloro-3,3,9-triethylthiacarbocyanine bromide.

3,3'-dialkyl 9 alkylselenathiacarbocyanine salt having the general formula:

wherein R, R' and R" each represent alkyl groups and X represents an acid radical, especially those dyes wherein R, R and R" each represent an alkyl group of the formula CnH2n+1 wherein n represents a positive integer of from 1 to 2, e. g., 3,3-diethyl-9-methylselenathiacarbocyanine iodide; 5-chloro-3,3'-diethyl-9-methylselenathiacarbocyanine iodide and 3,3'-diethyl-9-methylselenathiacarbocyanine bromide.

8,3'-dialkyl-9-alkylselenacarbocyanine salts having the general formula:

wherein R and R each represents an alkyl group and X represents an acid radical, especially those dyes where R and R each represents an alkyl group of the formula CnH2n+1 wherein n represents a positive integer of from one to two, e. g., 1,1diethyl-2,2-carbocyanine iodide; and

3,3-dia1kyl-9-alkyloxathiacarbocyanine and 3,3- dialkyl-Q-alkyloxaselenacarbocyanine salts havingthe general formula:

wherein R, R and R" each represent alkyl groups and X represents an acid radical, especially those dyes wherein R, R and R each represents an alkyl group of the formula CnHZn-l-l wherein n represents a positive integer of from one to 2, e. g., 3,3-diethyl-9-methyloxathiacarbocyanine iodide.

Our invention is primarily directed to the customarily employed gelatino-silver halide developing-out emulsions. However, silver halide emulsions in which the carrier is other than gelatin, e. g., a cellulose derivative or a resinous material, can also be employed.

Emulsions prepared in accordance with our inventlon can be coated in the usual manner upon any desired support, such as cellulose nitrate support, cellulose acetate support, polyvinyl acetal resin support, glass support, metal support or paper support.

The non-quaternary cyclammonium salts which we employ in practicing our invention, like the quaternary cyclammonium salts which we employ, can be prepared by heating the appropriate heterocyclic nitrogen base with esters (alkyl salts). For example, to prepare N-(fl-phenylethyl) piperidinium bromide, it is only necessary to heat piperldine with p-phenylethyl bromide.

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

1. A photographic silver halide emulsion selected from the group consisting of silver chlorobromide, silver bromide and silver bromiodide emulsions, containing in a concentration of from more than 0.2 gram to about 4 grams per grammole of silver halide in the emulsion, a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of cyclammonium quaternary salts and cyclammonium salts in which there is one hydrogen atom on the cyclammonium nitrogen atom and but two of the remaining valences of the cyclammonium nitrogen atom are employed in the formation of a cyclic nucleus, said cyclammonium salt containing not more than one quaternary nitrogen atom and containing only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined with said acid dye.

2. A photographic silver halid developing-out emulsion selected from the group consisting of silver chlorobromide developing-out emulsions, silver bromide developing-out emulsions and silver bromiodide developing-out emulsions, containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion. a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of cyclammonium quaternary salts and cyclammonium salts in which there is one hydrogen atom on the cyclammonium nitrogen atom and but two of the remaining valences of the cyclammonium nitrogen atom are employed in the formation of a cyclic nucleus, said cyclammonium salt containing not more than one quaternary nitrogen atom and containing only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom, any acid dye in said emulsion bein present in a concentration low enough that more than 0.2 gram of cyclammonium salt per grammole of silver halide in the emulsion is uncom bined with said acid dye.

3. A photographic silver halide developing-out emulsion selected from the group consisting of silver chlorobromide developing-out emulsions, silver bromide developing-out emulsions and silver bromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of cyclammonium quaternary salts and cyclammonium salts in which there is one hydrogen atom on the cyclammonium nitrogen atom and but two of the remaining valences of the cyclammonium nitrogen atom are employed in the formation of a cyclic nucleus, said cyclammonium salt containing not more than one quaternary nitrogen atom and containing only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined with said acid dye.

4. A photographic gelatino-silver-halide developing-out emulsion selected from the o p consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a substantially non surface active, substantially colorless cyclammonium salt selected from the group consisting of cyclammonium quaternary salts and cyclammonium salts in which there is one hydrogen atom on the cyclammonium nitrogen atom and but two of the remaining valences of the cyclammonium nitrogen atom are employed in the formation of a cyclic nucleus, said cyclammonium salt containing not more than one quaternary nitrogen atom and containing only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined with said acid dye.

5. A photographic silver halide emulsion selected from the group consisting of silver chlorobromide, silver bromide and silver bromiodide emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of cyclammonium quaternary salts and cyclammonium salts in which there is one hydrogen atom on the cyclammonium nitrogen atom and but two of the remaining valences of the cyclammonium nitrogen atom are employed in the formation of a cyclic nucleus, said cyclammonium salt containing not more than one quaternary nitrogen atom and containing only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom and being free from groups having the eifect of nitro, sulfonic acid and sulfonate groups, any acid dye in said emulsion being in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver halide in the emulsion are uncombined with said acid dye.

6, A photographic silver halide emulsion selected from the group consisting of silver chlorobromide, silver bromide and silver bromiodide emulsions, spectrally sensitized with nonacidic sensitizing dye containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of pyridine and quinoline quaternary salts, said cyclammonium salt containing not more than one quaternary nitrogen atom, any acid dye in said emulsion being in a concentration low enough that more than 0.2 gram of cyclammonium salt per grammole of silver halide in the emulsion are uncombined with said acid dye.

7. A photographic silver halide developingout emulsion selected from the group consisting of silver chlorobromide developing-out emulsions, silver bromide 'developing-out emulsions and silver bromiodide developing-out emulsions, spectrally sensitized with non-acidic sensitizing dye containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of pyridine and quinoline quaternary salts, said cyclammonium salt containing not more than one quaternary nitrogen atom, any acid dye in said emulsion being in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver' halide in the emulsion are uncombined with said acid dye.

8. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with non-acidic sensitizing dye containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a substantially non-surface active, substantially colorless cyclammonium salt selected from the group consisting of pyridine and quinoline quaternary salts, said cyclammonium salt containing not more than one quaternary nitrogen atom, any acid dye in said emulsion being in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver halide in the emulsion are uncombined with said acid dye.

9. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatinosilver-bromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in concentration of from more than 0.2 gram to about 4 grams per grammole of silver halide in the emulsion, a substan-- tially colorless cyclammonium salt selected from the group consisting of pyridine and quinoline quaternary salts, said cyclammonium quaternary salt containing not more than one quaternary nitrogen atom and being free from groups having the effect of nitro, sulfonic acid and sulfonate groups, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined with said acid dye.

10. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silverchlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye selected from the group consisting of oxacarbocyanine dyes, thiacarbocyanine dyes, selenacarbocyanine dyes, thiaselenacarbocyanine dyes, oxathiacarbocyaninedyes, oxaselenacarbocyanine dyes and 2,2'carbocyanine dyes, containing in a concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a non-surface active, substantially colorless cyclammonium salt selected from the group consisting of pyridine and quinoline quaternary salts, said cyclammonium quaternary salt containing not more than one quaternary nitrogen atom and being free from groups having the effect of nitro, sulfonic acid and sulfonate groups, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of cyclammonium quaternary salt per gram-mole of silver halide in the emulsion is uncombined with said acid dye.

11. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in a concentration of from than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion a non-surface active, substantially colorless cyclammonium aralkyl quaternary salt selected from the group consisting of pyridine and quinoline aralkyl quaternary salts, said cyclammonium aralkyl quaternary salt containing not more than one quaternary nitrogen atom and being free from groups having the effect of nitro, sulfonic acid and sulfonate groups, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of aralkyl cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined in said acid dye.

12. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in a concentraton of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion a non-surface active, substantially colorless cyclammonium pphenylethyl quaternary salt selected from the group consisting of pyridine and quinoline pphenylethyl quaternary salts, said cyclammonium p-phenylethyl quaternary salt containing not more than one quaternary nitrogen atom and being free from groups having the effect of .nitro, sulfonic acid and sulfonate groups, any

acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of p-phenylethyl cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined in said acid dye.

13. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye and containing in a concentration of from more than 0.2 gram to about Qgrams per gram-mole of silver halide in the emulsion a non-surface active, substantially colorless cyclammonium yphenyl-n-propyl quaternary salt selected from the group consisting of pyridine and quinoline 'y phenyl n propyl quaternary salts, said cyclammonium -phenyl-n-propyl quaternary salt containing not more than one quaternary nitrogen atom and being free from groups having the effect of nitro, sulfonic acid and sulfonate groups, any acid dye in said emulsion being present in a concentration low enoughthat more than 0.2 gram of y-DhEHYl-Il-DIOPYI cyclammonium salt per gram-mole of silver halide in the emulsion is uncombined in said acid dye.

14. A photographic gelatino-silver-halide developing-out emulsion selected from the group consisting of gelatino-silver-chlorobromide developing-out emulsions, gelatino-silver-bromide developing-out emulsions and gelatino-silverbromiodide developing-out emulsions, spectrally sensitized with a non-acidic sensitizing dye selected from the group consisting of oxacarbocyanine dyes, thiacarbocyanine dyes, selenacarbocyam'ne dyes, thiaselenacarbocyanine dyes, oxathiacarbocyanine dyes, oxaselenacarbocyanine dyes and 2,2'-carbocyanine dyes, containing in a, concentration of from more than 0.2 gram to about 4 grams per gram-mole of silver halide in the emulsion, a non-surface active, substantially colorless cyclammonium quaternary salt selected from the group consisting of pyridine and quinoline quaternary salts, said cyclammonium quaternary salt containing not more than one quaternary nitrogen atom and being free from groups having the effect of nitro, sulfonic and sulfonate groups, any acid dye in said emulsion being present in a concentration low enough that more than 0.2 gram of cyclammo- 10 nium quaternary salt per gram-mole of silver halide in the emulsion is uncombined with said acid dye.

BURT H. CARROLL. JOHN SPENCE.

H CERT]: FICATE 0F C0 RREC TI 0N Patent No. 2,55 h86h- November 25, 1915.

BURT H. CARROLL, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 211., for"interfacces" read "interfaces"; page 5, first column, line 60, Table L after 'silver" insert -halide--; line 61, for *senstiizers" read sensitiz ers; and that the said Letters Patent shouldbe' read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of February, A. D. 19%.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.