US2735769A

US2735769A - Stabilized photographic silver halede

Info

Publication number: US2735769A
Authority: US
Publication date: 1956-02-21
Anticipated expiration: 1973-02-21

Description

United States Patent STABILIZED PHOTOGRAPHIC' SILVER HALIDE EMULSIONS Charles F. H. Allen and Harry R. Beilfuss, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application July 1, 1953, Serial. No. 365,541

5 Claims. (Cl. 95-7) This invention relates to fog-inhibiting agents. and stabilizers for photographic emulsions and to photographic emulsions containing them.

It, is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without'exposure to light. There. is normally a detectable amount of the silver salt reduced during development in the areas Where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the efiects of accidental exposure to radiation; in this invention, we are not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases, with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is of course desirable to have. emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While anti-fog- 2,735,769 Patented Feb. 21, 1956 such as methyl, ethyl, n-propyl, isopropyl, n-butyl, noctyl, n-decyl, n-octad'ecyl, etc., an aryl group, such as phenyl, 0-, m-, and p-tolyl, naphthyl, etc. (e. g. a mononuclear aromatic group of the. benzene series), or a heterocyclic group, such as furyl, quinolyl, benzothiazolyl, pyridyl, etc. In general, the compounds represented by the above general formula can be prepared according to the method described in U. S. Patent 2,481,466, issued September 6, 1949. The method described in this patent consists in condensing a pyrazolone compound containing a primary amino group in the 3- position together with a diketene compound. Diketenes other than diketene itself can also advantageously be employed in preparing the compounds of the above gen; eral formula.

The quantity of antifoggant or stabilizing compound employed in practicing our invention is quite important in obtaining the results desired.v This is due, in part, to the presence of the reactive methylene groups as can be seen by reference to the above general formula. Accordingly, the quantity of antifoggant or stabilizing compound should not exceed 5 g. per mole of silver halide present in the photographic emulsion. Amounts varying from 0.01 to 3 g. per mole of silver halide have been found to be particularly useful in practicing our in,- vention.

The fog inhibitors which 'We propose to use are added to the emulsion during theprocess of manufacture, to avoid loss of sensitivity and to inhibit the growth of fog with passage of time under non-ideal conditions of storage.

gants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifogga-nt protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both. i

It is, accordingly, an object of our invention to provide a method for stabilizing photographic emulsions. A further object of our invention is to maintain the sensitivity and fog of silver halide emulsions at or close to initial optimum values under keeping'conditions of high temperature and humidity. A further object is to proide photographic silver halide. emulsions containing antigpggants or stabilizers. Other objects will become apparent from a consideration of the following description and examples.

The above objects are, in general, accomplished by adding to the photographic emulsion certain organic compounds of the following general formula:

wherein R represents an alkyl group, such as methyl, ethyl, n-propyl, isopropyl, etc., an aryl group, such as phenyl, o-, m and p-methoxyphenyl, o-, mand p-tolyl, etc. (e. g. a mononuclear aromatic group of the benzene series), or a heterocyclic group, such as furyl, quinolyl, benzothiazolyl, etc., and R1 represents an alkyl group,

A solution of the compounds of the invention when added in; suitable concentration, before coating, to unsensitized, chemically sensitized, or optically sensitized photographic emulsions does not appreciably aifect the? sensitometric values for sensitivity and fog when measurements are made soon after coating. When sensitometric measurements are made at appreciable intervals of time, at elevated temperatures. and dry or somewhat humid conditions, these compounds do stabilize photographic speed and maintain fog at a low level.

The preparation of silverxhalide 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, and (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 afterripening, although they can advantageously be added prior to digestion.

Listed below are a number of compounds coming within the scope of the above general formula, which we have found to be particularly advantageous in practicing our invention. These compounds belong to a group of compounds which we shall designate as triazaindenes.

1. H: CH:

3. 1% N 0=o J-d/H:

1,2,'3,5-tetrahydro-2,5-diketo-l,7-dimethyl-L4,7a-triazaindene 2. CH1; (luH 1,'2,3,5=tetrahydro-2,5-dlketoJ-methyl-1-phenyl-1,4,7a* v. i triazetndene- 1,2,3,5-tetrahydro-2,5-di1reto-1,7-dipheny1-1,4,7a-triazaindeno olie 11:

1,2,3,5-tetrahydro-,5-diket0-7-o-methoxyphenyl-1-pl1eny1- 1,4,7a-triazaindene 1,2,3,5-tetrahydro-2,5-diketo-7-m-methoxyphenyl-1-phenyl- 1,4,711-triazaindene H =0 CIHB 1,2,3,5-tetrahydro-2,5-diket0-7-a-fury1-1-phenyl-1,4,7atriazaindene 1,2,3,5-tetrahydro-2,5-diket0-7-methyl-'1-(2-quinolyl)- 1,4,7 a-triazaindene H0 N C=0 O=\ N 1,2,3,5-tetrahydro-2,5-diketo-1- (2'benzothlazolyl) -7-methyl- 1,4,7a-triazaindene The photographic emulsions used in practicing our invention are generally of the developing-out type; also, it is to be understood that photographic emulsions of varying halide content can advantageously be used. The antifoggant compounds used in our invention have been found particularly useful when employed in conjunction with gelatino-silver bromiodide emulsions, although they can also be advantageously employed for stabilizing other silver halide emulsions, such as gelatino-silver chloride, bromide, chlorobromide, chlorobromiodide, etc. The emulsions can be unsensitized, or sensitized with chemical sensitizers or optical sensitizers. Sulfur sensitizers, such as those disclosed in Sheppard U. S. Patent 1,574,944 can advantageously be added to the emulsions in theconventional manner. Also, various gold sensitizers can be employed in the photographic emulsions stabilized according to our invention.

The efficiency of the antifoggant or stabilizing agent was determined by incubation of the emulsions for three days at a temperature of 120 F. and a humidity of 45 percent. The eflicieney was determined by measuring the speed, gamma and fog of the incubated emulsions containing an antifoggant and comparing these measurements with those of the same batch of emulsion before incubation. Also, similar measurements were made on the same batch of photographic emulsion containing no antifoggant, both before and after incubation. The tests were made using a high speed silver bromiodide emulsion exposed on an Eastman Type Ib sensitometer and developed for 6 /2 minutes in a developer of the following composition:

grams N-methyl p-aminophenyl sulfate 1.5 Hydroquinone 1.3 Sodium sulfite (desiccated) Borax 4.5 Potassium bromide 0.4

Water to one liter Fresh Test Incubation Test Ex. Antiloggant g./mole No. Compound AgX 10H 10 speed 7 Fog speed 7 Fog 1(a)-- None 3,800 0. 75 10 2, 600 0.69 24 (0)...- Compound 6 0. 6 3, 450 0. 89 09 3, 350 0. 74 l4 2(a) Same as 101).. (10.... Compound 5.. 0 6 3,600 0.73 08 3,500 0.72 .12

In a manner similar to that illustrated in the above examples, other compounds coming within the scope of the above general formula can be incorporated in photographic emulsions for the purpose of stabilization. The fog-inhibiting agents useful in practicing our invention can be used in various kinds of photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions, they can also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they can be added to the emulsion before or after the dyes are added. Suitable dispersing agents for the silver halide comprise gelatin, or other colloids, such as collodion, albumen, cellulose organic derivatives, synthetic resins, etc.

Instead of adding the fog-inhibiting agent directly to the photographic emulsion, it is sometimes desirable to incorporate the fog-inhibiting agent in a separate layer which is placed in contact wtih the silver halide emulsion layer. Under such conditions, of course, it is desirable to use a higher concentration of fog-inhibiting agent than indicated above in the separate layer, which generally contains no silver halide.

We have also found that compounds selected from those of the above general formula wherein R represents a hydroxyl group can also be used for the purpose of stabilizing photographic emulsions. Such compounds can be formulated in their keto form, or in their enol form.

For example, the compound having the following formula has been found to be useful as an antifoggant.

2,5,7-triketo-l-phenyl-1,2,3,5,6,7-hexahydro-1,4,7a-triazaindene It will be noted that the above compound has been written in its keto form. Also such a compound can be written with a hydrogen atom of the methylene group being attached to one of the oxygen atoms of one of the keto.

Example 3.2,5-diketo-1-phenyl-7-(o-methoxyphenyl) -1,4,7a-triazaindene -c oorno 0.0.11 niN-o orn In a flask fitted with a 10-in. steam jacketed column terminating in a still head fitted with a thermometer and connected to a water cooled condenser, were placed g. (0.08 mole) of ethyl o-methoxybenzoylacetate and 35 cc. of xylene. The solution was heated to boiling, 8.75 g. (0.05 mole) of 1-phenyl-3-amino-5-pyrazolone were added, and the mixture was heated for 1.5 hours, at 145-160 C. The temperature of the distillate varied between 7 5-95 C. while the water and alcohol were distilling, and finally rose to 140 C. at the end of the reaction. The distillate collected (7.5 cc.) was a mixture of water, alcohol and xylene. On cooling the solution, the product crystallized. It was filtered and washed with alcohol, yield, 7.9 g.; M. P. 2l0212 C.

Example 4.2,5-diketo-1-phenyl-7-(m-methoxyphenyl) -1,4,7a-triazaindene has This compound was prepared in a manner similar to Example 3, from ethyl m-methoxybenzoyl acetate and 1-phenyl-3-amino-5-pyrazolone. It was obtained in a 65% yield,.M. P. 254255 C.

What We claim as our invention and desire secured-by Letters Patent of the United States is:

1. A photographic silver halide emulsion containing from 0.01 to 5.0 g. per mole of silver halide of a compound selected from those represented by the following general formula:

and

wherein R and R1 each represents a member selected from the group consisting of an alkyl group, an aryl group and a heterocyclic group.

2. A photographic silver halide emulsion containing from 0.01 to 3.0 g. per mole of silver halide of a compound selected from those represented by the following general formula:

wherein R and R1 each represents a mononuclear aromatic group of the benzene series.

3. A photographic silver bromiodide emulsion containing from 0.01 to 3.0 g. per mole of silver halide of a compound selected from those represented by the following general formula:

4.A photographic silver halide emulsion containing from 0.01 to 3.0 g. per mole of silver halide of a compound having the following formula:

CHaO

CQH5

5. A photographic silver halide emulsion containing from 0.01 to 3.0 g. per mole of silver halide of a com- 7 pound having the following formula:

OCH1

GcHI 0=l\ -(5Hg References Cited in the file of this patent UNITED STATES PATENTS 2,350,138 Weissberger May 30, 1944' 2,449,225 Heimbach et a1 Sept. 14, 1948 2,450,397 Heimbach Sept. 28, 1948 2,481,466 Bavley Sept. 6, 1949 OTHER REFERENCES Wall: Photographic Emulsions. Pub. by American Photographic Publishing C0,, Boston, 1929, pages 324 and 325.

Claims

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING FROM 0.001 TO 5.0 G. PER MOLE OF SILVER HALIDE OF A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: