US3232762A - Bromoacylurethans as antifoggants - Google Patents

Description

United States PatentO 3,232,762 BROMOACYLURETHANS AS AN'IIFOGGANTS John- A. Ford, Jr., and Charles V. Wilson, Rochester,

N.Y., assiguors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing Filed July 3, 1963, Ser. No. 292,762 13 Claims. (Cl. 96109) 1 This invention relates to fog-inhibiting agents for photographic emulsions and to photographic emulsions containing them.

It is well known that photographic emulsions on storage" tend to lose sensitivity and to becomespontaneously developable without exposure to light. There is normally' a detectable amountof the silver salt reduced during development in the areas where no exposure was given;' this is commonly c'alledfog, 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 atincreased 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 is frequently 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 antifoggants may protect, to some extent, against such effects, it is normally understood that an antifoggant 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.

It is, accordingly, an object of our invention to provide a new method for stabilizing photographic silver halide emulsions.

A- further object is to provide novel photographic silver halide emulsions containing antifoggants or stabilizers.

It is another object of our invention to provide novel photographic silver halide emulsions that are stabilized with antifoggant addenda that do not objectionably desensitize the emulsions.

Other objects will become apparent from a consideration of the following description and examples.

According to our invention, photographic silver halide emulsions are stabilized with an alkyl bromoacylurethan. These compounds can be represented by the following general formula:

where n has a value of 1 to 7 inclusive, and R represents a member selected from the group consisting. of an alkyl radical such as ethyl, butyl, octyl, etc. and a haloalkyl radical such as bromoethyl.

It has also been found in certain instances that a number of the compounds embraced by Formula I above serve to increase the sensitivity of photographic silver halide emulsions, in addition to stabilizing the emulsions or providing an anti-foggant effect. However, the

'25, 279281 (1960). isomerizing N-bromosuccinimide to 3-bromopropionyl 3,232,762 Patented Feb. 1,1966

fog-inhibiting effect is more general than the sensitizing efiect,and for this reason, these compounds are referred tobelow as antifoggants or fog-inhibitors.

The fog-inhibitors of our invention can be added to the emulsion during the process of manufacture, either during mixing, ripening, or after-ripening, in order to avoid loss of sensitivity and/ or to inhibit the growth of fog with the passage of time under non-ideal conditions of storage.

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

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silverhalide, (2) the freeing of theemu-lsion 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 (1952).) We prefer to add the fog-inhibiting agents after the final digestion or afterripening, although they-can advantageously be added prior to digestion. If desired, the fog-inhibiting agents of our invention can be-incorporated in the emulsions without adverse effects by the bathing techniques known to those skilled in the art.

Listed below are a number of compounds coming within the-scope of Formula I above which are typical of the antifoggants of our invention.

Butyl 3-bromopropionylurethan Octadecyl-3-bromopropionyluretl1an Many of the compounds embraced by Formula I ....above..have been previously described in the prior art.

These compounds can be prepared according to the procedure described by Johnson et al. in J. Org. Chem., This method, briefly, comprises isocyanate which without isolation is treated with an alcohol to give the corresponding alkyl-3-bromopropionylurethan. Another method of preparing the antifoggants of this invention, given in J. Org. Chem, 27, 3742 (1962), involves the reaction of oxalyl chloride upon an amide to form an acyl isocyanate which is again treated with an alcohol to form the corresponding acyl urethan.

at preparation.

EXAMPLE 1 A mixture of 250 ml. of chloroform, 26.7 g. of N- orom'osuecinimide, 1 ml. of allyl chloride, and 5 mg. of oenzoyl peroxide was refluxed with stirring for 4 hours. The resulting solution was cooled to room temperature, treated with a solution of 28.4 g. of l-octadecanol in 100 ml. of chloroform and cooled overnight in a freezer. The solid which separated was filtered and dried. Re- :rystallization from ethyl acetate gave 28 g. of colorless :rystals of octadecyl-3-bromopropionylurethan having a melting point of 97-98 C. This melting point agrees exactly with that reported in the literature [Johnson et 11., J. Org. Chem, 25, 279, 280 (1960)].

EXAMPLE 2 A mixture of 11.7 g. of 6-bromocaproamide, 7.7 g. of Jxalyl chloride, and 140 ml. of 1,2-dichloroethane was refluxed for 6 hours, cooled to room temperature, treated with 2.8 g. of ethanol, and allowed to stand overnight. The solid thus formed was filtered, and recrystallized once from ligroin and twice from cyclohexane to give 7.5 g. )f colorless crystals of ethyl-6-bromocaproylurethan havng a melting point of 78-8l C.

Analysis.Calcd. for C H BrNO z C, 40.6%; H, 3.02%. Found: C, 41.0%; H, 6.1%.

The photographic emulsions used in practicing our in- Iention are generally of the developing-out type Various silver salts may be used as the sensitive salt 11 preparing the present emulsions such as silver bromide, :ilver iodide, silver chloride, or mixed silver halides such is silver chlorobromide, silver bromoiodide and the like.

In the preparation 'of the silver halide dispersions emloyed for preparing silver halide emulsions, there may e employed as the dispersing agent for the silver halide it its preparation, gelatin or some other hydrophilic coloidal material such as colloidal albumin, a cellulose lerivative or a synthetic resin, for instance, a polyvinyl :ompound. Some colloids which may be used are loly(vinyl alcohol) or a hydrolyzed poly(vinyl acetate) lS described in Lowe US. Patent 2,286,215, issued June .6, 1942.

The emulsions of the invention can contain convenional photographic silver halide emulsion addenda such 18 optical sensitizers, chemical sensitizers, coating aids, gelatin hardeners, plasticizers, and the like, as well as ither antifoggants in conjunction with the present antioggants.

The present photographic emulsions of the invention :an be coated on any of the conventional photographic supports including paper, cellulose, acetate film, poly:

ethylene film, polyethyleneterephthalate film, polystyrene film, glass and the like.

The optimum amount of fog-inhibiting agent can be determined by making the customary tests employed in emulsion making. Of course, the optimum ,amountfor a given emulsion will vary dependingon the presence of emulsion addenda, such as chemical 'sensitizers, optical sensitizers, etc. In general we have found that from about .01 to about 20 g. of fog-inhibiting agent per mole of silver halide is suitable for the purpose of our invention, with a preferred range of from about .1 ,toabout 10 g. of fog-inhibiting agent per mole of silver halide; Instead of adding the fog-inhibiting agent directly to the. photographic emulsion, it is sometimes desirable to.in-" corporate the fog-inhibiting agent in a separate water-. permeable hydrophilic colloid layer which is contiguous? with the silver halide emulsion layer which is to be stabilized. In such embodiments of the invention we prefer to use the higherconcentrations of fog-inhibiting agents.

The present invention is further illustrated by the folthe various tested antifoggants was determined by meas uring 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 with a photographic emulsion containing no anti-L The tests foggant both before and after incubation. were made using high speed, negative-type silver brom'oiodide emulsions (coated on cellulose acetate supports),

which had been panchromatically sensitized with cyanine.

dyes. The test films were exposed onan intensity scale sensitometer (Kodak Type Ib) and developed for 5 minutes at 68 F. in the following composition:

, I Gms. p-Methylaminophenol sulfate 2.5 Sodium sulfite, desiccated 30.0' Hydroquinone v 2.5 Sodium metaborate, octahydrate 10.0

Potassium bromide Water to make 1 liter.

The speed, gamma and fog for each of the emulsioncoatings were then measured as indicated above. The 7 results obtained are given in the following tables.

Table I Com- Cnncen- Fresh Coatings Incubated Coatings Example pound tration,

No. gmslmole AgX Speed Gamma Fog I Speed Gamma Fog Control 160 0. 9O 0. 1O 0. 73 0. 28

Table II Fresh Coatings Incubated Coatings Comt-i Concentrai Exam le oun tion, gms.

p N mole gX Speed Gamma Fog Speed Gamma Fog II t Br(oH2),,oNHC-oR wherein n is an integer of 1 to 7 and R is an alkyl radical. 3. A photographic silver halide emulsion containing an antifoggant compound having the formula:

wherein R is an alkyl radical having 1 to 18 carbon atoms.

4. A photographic gelatino silver halide developing-out emulsion containing from about .01 g. to about 20 g. per mole of silver halide of an antifoggant having the following formula:

Br(oHz)riiNHooGH2-omBr 5. A photographic gelatino silver halide developing-out emulsion containing from about .01 g. to about 20 g. per mole of silver halide of an antifoggant having the following formula:

6. A photographic gelatino silver halide developing-out emulsion containing from about .01 'g. to about 20 g. per mole of silver halide of an antifoggant having the following formula:

7. A photographic gelatino silver halide developing-out emulsion containing from about .01 g. to about 20 g. per

6 mole of silver halide of an antifoggant having the following formula:

Br(CH2)2-%NH%O(CH2)11-CH 9. A photographic gelatino silver halide developing-out emulsion containing from about .01 g. to about 20 g. per

mole of silver halide of an antifoggant having the following formula:

10. A photographic element comprising a photographic silver halide emulsion layer and a contiguous water-permeable hydrophilic colloid layer, at least one of said layers containing an alkyl(monobromoalkanoyl)urethan.

=11. A photographic silver halide emulsion as described in claim 2 wherein the silver halide is silver brornoiodide.

12. A photographic silver halide emulsion as described in claim 2 wherein the R substituent of the antifoggant compound is a haloalkyl radical.

1?. A photographic silver halide emulsion as described in claim 3 wherein the R substituent of the antifoggant compound is a bromoalkyl radical having 1 to 18 carbon atoms.

References Cited by the Examiner NORMAN G. TORCHIN, Primary Examiner.

Claims (1)

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING AN ALKYL(MONOBROMOALKANOYL)URETHAN ANTIFOGGANT.