Compounds of the general formula: ##STR1## wherein X is cyano or ##STR2## Q is OR.sub.1 or --NR.sub.2 R.sub.3 ; R.sub.1 is hydrogen or alkyl of 1-4 carbon atoms, R.sub.2 is hydrogen or methyl, and R.sub.3 is hydrogen or alkyl of 1-4 carbon atoms, are incorporated into light sensitive silver halide emulsions to improve their sensitometric characteristics.

FIELD OF INVENTION 
This invention is directed to photographic materials comprising 
light-sensitive silver halide emulsions and, in particular, to stabilized 
silver halide emulsions containing an effective antifoggant. 
BACKGROUND OF THE INVENTION 
Gelatino-silver halide emulsions are subject to fogging, which may be 
defined as a uniform deposit of silver extending over, and either 
partially or wholly obliterating, the image. Fog may be caused in a number 
of ways, as for example, by excessive ripening of the emulsion, by storage 
of the light-sensitive element at elevated temperatures and humidity, or 
by prolonged development of the exposed emulsion. 
A great number of antifogging and stabilizing agents have been recommended 
in the literature for the purpose of preventing the formation of fog in 
light-sensitive silver halide emulsions. Although these compounds have the 
ability to control fog during manufacture, as well as during storage, many 
of these compounds adversely affect other sensitometric properties such as 
speed, gradient and Dmax. It is, accordingly, an object of this invention 
to provide a light-sensitive emulsion which has a reduced tendency to fog; 
but at the same time retains a good balance of other sensitometric 
properties. 
SUMMARY OF THE INVENTION 
A tetrathiocino diisothiazole of the formula 
##STR3## 
wherein X is cyano or 
##STR4## 
Q is --OR.sub.1 or --NR.sub.2 R.sub.3 ; R.sub.1 and R.sub.3 are hydrogen 
or alkyl of 1-4 carbon atoms, and R.sub.2 is hydrogen or methyl, is 
incorporated into a photographic element comprising a light-sensitive 
silver halide emulsion layer on a support. It is preferred to add these 
compounds to the silver halide emulsion, but it is also possible to 
incorporate them into an auxiliary layer which may or may not be 
contiguous to the emulsion layer. These compounds act as antifoggants by 
restraining fog growth; but at the same time, act as development 
accelerators by increasing gradient and Dmax, usually at some speed loss. 
DETAILED DESCRIPTION OF THE INVENTION 
The tetrathiocino diisothiazoles may be added to silver halide emulsions 
during the digestion stage of preparation of said emulsions or as a final 
addition just prior to coating the silver halide emulsion onto a support. 
There is some indication that the presence of these compounds during 
digestion allows greater fog reduction than addition as a final just prior 
to coating, which suggests that these compounds may be interfering with 
the formation of fog centers, as well as covering up centers already 
formed, or preventing development of fog centers. It is believed that the 
tetrathiocino portion of the molecule may be a more important part for 
antifogging than the isothiazole. These compounds may also be used in 
combination with other known antifoggants, which are usually added as 
final additions just prior to coating the silver halide emulsions onto a 
support. In general, these compounds are added to a silver halide emulsion 
after it has been chemically sensitized with a conventional gold, sulfur 
and/or reduction sensitizer.

Among the tetrathiocino diisothiazole compounds suitable for this invention 
the following are illustrative: 
Compound 1 
##STR5## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarbonitrile 
Compound 2 
##STR6## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxylic 
acid dimethyl ester 
Compound 3 
##STR7## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxylic 
acid diethyl ester 
Compound 4 
##STR8## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxylic 
acid diisopropyl ester 
Compound 5 
##STR9## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxylic 
acid di n-butyl ester 
Compound 6 
##STR10## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxamide 
Compound 7 
##STR11## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxamide, 
N,N'-dimethyl 
Compound 8 
##STR12## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxamide, 
N,N,N', N'-tetramethyl 
Compound 9 
##STR13## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxamide, 
N,N'-diethyl 
Compound 10 
##STR14## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxamide, 
N,N'-diisopropyl 
Compound 11 
##STR15## 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarboxamide, 
N,N'-di-n-butyl 
These compounds may be incorporated into any type of light-sensitive silver 
halide emulsion layer, e.g., a spectrally sensitized or nonsensitized 
silver halide layer, a radiographic emulsion layer, and a high speed 
negative or positive light-sensitive emulsion. Of course, the amount to be 
added will vary dependent on the particular type of emulsion and can vary 
within wide limits. Enough compound is added to the emulsion to give good 
antifoggant properties without significant change in other photographic 
properties like speed, gradient or Dmax. Optimum amounts to be added can 
be determined for each emulsion by simple experiment as is customary in 
the art of emulsion manufacture. Generally, the most suitable 
concentration will be between 1.6.times.10.sup.-6 mole to 
1.7.times.10.sup.-4 mole per 1.5 moles of silver halide in the emulsion. 
However, greater or lesser amounts can be used. 
[1,2,5,6] tetrathiocino [3,4-c; 7,8-c'] diisothiazole-3,8-dicarbonitrile 
was prepared by the procedure described in Vladuchick, U.S. Pat. No. 
4,066,656 "[1,2,5,6]Tetrathiocino-[3,4-C; 
7,8-C']Diisothiazole-3,8-Dicarbonitrile". The dicarboxylic acid was 
prepared from the dicarbonitrile by base hydrolysis while the amides and 
esters were prepared via reaction with the acid chloride by standard 
manipulation. 
The silver halide constituent of the light-sensitive silver halide emulsion 
may be any of the usual types such as silver chloride, silver bromide, 
silver iodide or solid solutions thereof, in the form of single salt or 
mixed silver halide grains or crystals e.g. silver chromobromide, silver 
iodobromide, etc. These can be doped with other metal cations such as 
divalent lead or tin. These silver halide emulsion grains may be 
chemically sensitized with noble metal salts and labile sulfur compounds, 
e.g., gold chloride and sodium thiosulfate, as commonly practiced in the 
art of emulsion manufacture. Other addenda such as hardeners, wetting 
agents and plasticizers may be added in the usual manner. 
Gelatin is the preferred binder for the silver halide grains, but it may be 
partially replaced with other material or synthetic binders as known in 
the art. Thus, binders used to increase covering power, e.g., dextran, 
dextrin, polyvinyl pyrrolidone, etc., as well as latices of polymers such 
as poly (ethyl acrylate) which are useful in improving dimensional 
stability and other physical properties are advantageously included in 
silver halide emulsions used in this invention. 
The silver halide elements of this invention may include one or a plurality 
of emulsion layers, and may be coated on a support such as glass, paper or 
polymeric film (e.g., a polyester film). 
Silver halide emulsions were prepared according to the following 
procedures. 
Procedure A: Silver Iodobromide Emulsion 
A gelatino-silver iodobromide emulsion containing 1.27% iodide was made by 
adding aqueous silver nitrate solution in two equal portions to an aqueous 
gelatin solution containing the required amount of potassium iodide and 
bromide. The precipitation was carried out at 114.5.degree. F. 
(45.8.degree. C.). After the first silver nitrate addition, the emulsion 
was ripened 12 minutes; and after the second addition, it was ripened for 
6 minutes in the presence of sufficient ammonia to convert 13% of the 
silver present and the ammonia was then neutralized with sulfuric acid. 
The emulsion was then cooled, coagulated, washed and redispersed in a 
conventional manner. 
Procedure B: Monodisperse Silver Iodobromide Emulsion 
A gelatino-silver iodobromide emulsion containing 1.5 mole % iodide was 
made by a balanced double-jet method in which both soluble silver nitrate 
and alkali metal iodobromide salts were added to an aqueous ammoniacal 
gelatin solution at a temperature of 115.degree. F. (46.1.degree. C.) and 
at a constant pAg of 8.35 to produce cubic silver iodobromide grains 
having a mean grain volume of 0.031 cubic microns and a narrow grain size 
distribution. The emulsion was freed from soluble salts by lowering the pH 
to 2, cooling the emulsion to 85.degree. C., coagulating with 500 ml of a 
solution of a water-soluble o-sulfobenzaldehyde partial acetal of 
polyvinyl alcohol, and washing. 
Procedure C: Negative Type Emulsion Digestion 
To an emulsion containing silver halide equivalent to 1.5 moles of silver 
nitrate and prepared by Procedure A above there was added bulking gelatin 
and the temperature was raised to 110.degree. F. The pH was adjusted, the 
emulsion was heated to 125.degree. F. (51.7.degree. C.) and there was 
added 1.6.times.10.sup.-5 mole of a conventional sulfur sensitizer (sodium 
thiosulfate), 5.28.times.10.sup.-6 mole of gold in the form of HAuCl.sub.4 
and 3.81.times.10.sup.-3 mole of KSCN, a gold complexing compound. 
The emulsion was then digested for 120 minutes at 125.degree. F. 
(51.7.degree. C.), and was then optically sensitized. The pH was then 
adjusted to 5.5, and a coating aid was added, along with formaldehyde as 
the gelatin hardener. The compounds of this invention were now added to 
the emulsion. The latter was then coated upon a photographic quality 
poyethylene terephthalate film base and dried in conventional manner. Said 
film base had been first coated on both sides with a vinylidene 
chloride-alkyl acrylate/itaconic acid copolymer mixed with an alkyl 
acrylate. Over this there had been coated on both sides a thin anchoring 
substratum of gelatin (0.5 mg/dm.sup.2). 
Procedure D: Negative Type Emulsion Digestion 
To an emulsion containing the silver halide equivalent of 1.5 moles silver 
nitrate, and prepared by Procedure B above, there was added bulking 
gelatin and the temperature raised to 110.degree. F. (43.3.degree. C.). 
The pH was adjusted to 6.3, the emulsion heated to 130.degree. F. 
(54.5.degree. C.), and there was added 4.6.times.10.sup.-6 mole of gold in 
the form of AuCl.sub.3, 3.2.times.10.sup.-5 mole of sodium thiosulfate, 
and 1.4.times.10.sup.-3 mole of KSCN. The emulsion was digested for 35 
minutes at 130.degree. F. (54.5.degree. C.). After digestion, a coating 
aid and a gelatin hardener were added to the emulsion, the emulsion was 
cooled to 95.degree. F. (35.degree. C.) and the pAg was adjusted to 9.1. 
The tetrathiocino diisothiazole compounds were now added to the emulsion. 
This was then coated on a polyester support, similar to that described in 
Procedure C, to provide a coating of 75 mg of silver halide per dm.sup.2, 
and dried in a conventional manner. 
Coated and dried samples were tested, fresh (F) and after being oven aged 
(0) for 7 days at 120.degree. F. and 65% relative humidity, using the 
methods described below: 
Method 1 
A coated and dried sample was exposed for 10.sup.-4 seconds in a 
sensitometer, through a .sqroot.2 step wedge, by means of a lamp which 
provided an exposure of 130 meter-candle-seconds, developed for 60 seconds 
at 80.degree. F. (26.7.degree. C.) in a conventional 
hydroquinone-phenidone type developer, fixed, washed and dried. 1X/3X fog 
samples were processed for 1 minute and 3 minutes as above with no 
exposure. 
Method 2 
A coated and dried sample was exposed for 10.sup.-2 seconds in a EG&G. Mark 
VI Xenon Sensitometer through a 1.6 neutral density filter, and developed 
in a hydroquinone/phenidone type developer, fixed, washed and dried. 
Method 3 
Method 1 was repeated but with a K-2 filter to measure response to exposure 
in the green. 
EXAMPLE 1 
Gelatino-silver iodobromide emulsions were prepared as described in 
Procedure A, digested and coated as in Procedure C with the pH adjusted to 
5.61, and tested as described in Methods 1 and 3. Varying amounts of 
Compound 1, indicated in Table 1, were also added to the emulsions as 
final additions just prior to coating. Results are shown in the following 
table. 
Table 1 
__________________________________________________________________________ 
Amt. in 
Moles of 
Compound 1 
Method #1 Method #3 Per 1.5 
Rela- Rela- 
Moles of 
Ctg. 
Test 
1X/3X D- tive D- tive 
Silver 
# Age 
Fog Fog 
Max 
Speed 
Fog 
Max 
Speed 
Halide 
__________________________________________________________________________ 
1 F 04/09 
.04 
3.02 
190 .05 
2.62 
174 None 
0 06/15 
.05 
2.76 
155 .05 
2.29 
111 
2 F 03/05 
.03 
3.11 
173 .03 
2.79 
167 1.6 .times. 10.sup.-6 
0 03/07 
.04 
2.87 
174 .04 
2.45 
120 
3 F 01/02 
.01 
3.05 
175 .01 
2.62 
169 8.5 .times. 10.sup.-6 
0 01/02 
.01 
2.83 
167 .02 
2.41 
105 
4 F 00/01 
.00 
3.07 
164 .01 
2.85 
165 1.7 .times. 10.sup.-5 
0 00/01 
.01 
2.87 
155 .01 
2.44 
105 
5 F 00/00 
.00 
3.03 
150 .00 
2.63 
131 3.4 .times. 10.sup.-5 
0 00/01 
.00 
2.77 
154 .00 
2.35 
94 
6 F 00/00 
.00 
2.81 
137 .00 
2.63 
112 1.7 .times. 10.sup.-4 
0 00/01 
.00 
2.77 
138 .00 
2.25 
88 
7 NA 03/04 
.04 
2.50 
100 .03 
2.26 
100 None 
__________________________________________________________________________ 
EXAMPLE 2 
Gelatino-silver iodobromide emulsions were prepared as described in Example 
1, with the following variations: 1.6.times.10.sup.-6 mole of tert.-butyl 
diphenyl methyl trithiocarbonate was added and the pH adjusted to 5.52 
before digestion. Compound 1 was added, as a final addition just prior to 
coating, in amounts indicated in Table II. Results are shown in the 
following Table. 
Table II 
__________________________________________________________________________ 
Moles of 
Compound 1/1.5 
Rela- 
Moles of 
Ctg. 
Test 
1X/3X D- D- tive 
Silver 
# Age 
Fog Fog 
Max 
Speed 
Fog 
Max 
Speed 
Halide 
__________________________________________________________________________ 
1 F 06/12 
.07 
3.20 
183 .07 
2.62 
166 None 
(Control) 
0 08/22 
.11 
2.88 
146 .09 
2.39 
105 
2 F 03/05 
.03 
3.13 
177 .03 
2.79 
146 1.6 .times. 10.sup.-6 
0 03/06 
.05 
3.03 
158 .04 
2.52 
102 
3 F 01/03 
.02 
3.16 
173 .01 
2.62 
131 8.5 .times. 10.sup.-6 
0 01/03 
.01 
2.96 
139 .02 
2.56 
93 
4 F 00/01 
.00 
3.18 
139 .00 
2.85 
122 1.7 .times. 10.sup.-5 
0 00/02 
.01 
3.11 
167 .00 
2.52 
91 
5 F 00/00 
.00 
3.13 
140 .00 
2.63 
109 3.4 .times. 10.sup.-5 
0 00/00 
.00 
3.02 
152 .00 
2.40 
92 
6 F 00/00 
.00 
3.15 
131 .00 
2.63 
98 1.7 .times. 10.sup.-4 
0 00/00 
.00 
3.02 
144 .00 
2.48 
89 
7 NA 03/04 
.04 
2.50 
100 .03 
2.26 
100 None 
__________________________________________________________________________ 
cl EXAMPLE 3 
Example 1 was repeated with the variations in digestion pH and antifogger 
addition indicated in Table III. Compound 1 gives reduced fog with little 
reduction in speed for both the fresh and oven aged samples. 
Table III 
__________________________________________________________________________ 
Moles of 
Compound 
1/1.5 
Rela- Rela- Moles of 
Ctg. 
Test 
1X/3X D- tive D- tive 
Dig. 
Silver 
# Age 
Fog Fog 
Max 
Speed 
Fog 
Max 
Speed 
pH Halide 
__________________________________________________________________________ 
1 F 02/06 
.03 
3.17 
170 .03 
2.76 
182 5.3 
None 
0 04/08 
.06 
3.22 
187 .05 
2.72 
171 
2 F 00/01 
.01 
2.93 
160 .00 
2.50 
135 " 1.7 .times. 10.sup.-5 
0 00/01 
.01 
3.00 
159 .00 
2.68 
139 
3 F 00/02 
.03 
3.04 
160 .02 
2.52 
159 5.5 
None 
0 04/08 
.05 
2.88 
152 .05 
2.35 
141 
4 F 00/00 
.00 
3.25 
152 .00 
2.59 
136 5.5 
1.7 .times. 10.sup.-5 
0 00/01 
.00 
3.25 
156 .00 
2.76 
127 
5 F 00/05 
.04 
3.56 
186 .03 
3.19 
189 5.7 
None 
0 06/15 
.07 
3.25 
184 .07 
3.04 
188 
6 F 00/00 
.01 
3.38 
172 .01 
2.60 
147 " 1.7 .times. 10.sup.-5 
0 01/03 
.02 
3.37 
175 .01 
3.01 
160 
__________________________________________________________________________ 
EXAMPLE 4 
Example 1 was repeated with the variations in antifogger addition indicated 
in Table IV. The emulsions were digested at a pH of 5.5. Results are shown 
in the following table. 
Table IV 
______________________________________ 
Moles of 
Antifogger/1.5 
Moles of 
Silver Halide 
4 
hydroxy- 
6-methyl- 
1,3,3a,7 
Rela- tetra- 
Ctg. Test 1X/3X D- tive azain- Compound 
# Age Fog Fog Max Speed dene 1 
______________________________________ 
1 F 18/28 .18 2.66 133 None None 
(Control) 
2 F 17/27 .12 2.53 126 4.6 .times. 
None 
(control) 
10.sup.-2 
3 F 03/08 .03 2.56 106 4.6 .times. 
1 .times. 10.sup.-5 
10.sup.-2 
4 F 00/02 .00 2.43 33 4.6 .times. 
1 .times. 10.sup.-4 
10.sup.-2 
5 F 04/10 .02 2.85 105 None 1 .times. 10.sup.-5 
6 F 00/02 .00 3.05 60 None 1 .times. 10.sup.-4 
______________________________________ 
The results show that the tetraazaindene compound is not needed for good 
antifogging when the compounds of the invention are used. 
EXAMPLE 5 
Example 1 was repeated with variations in the antifogger addition indicated 
in Table V. 
Table V 
______________________________________ 
Ctg. 1X/3X D- Moles of Compd. 1/1.5 
# Dev. Fog Fog Max Speed Moles of Silver Halide 
______________________________________ 
1 20/44 .18 2.92 126 Control - None 
2 12/33 .12 3.12 131 1.7 .times. 10.sup.-5 as a final 
3 08/22 .07 3.02 126 1.7 .times. 10.sup.-5 at 
______________________________________ 
digest 
The control shows high fog. Fog is reduced when Compound 1 is added as a 
final addition just prior to coating, and further reduced when the 
antifogger is added during digestion. 
EXAMPLE 6 
Silver iodobromide emulsions were prepared as described in Procedure B and 
digested as in Procedure D. Compound 8 was added to the emulsion, as a 
final addition just prior to coating, in amounts indicated in Table VI. 
Table VI 
______________________________________ 
Grams Compd. 8 
Rela- Development 
Ctg. Per 1.5 Moles 
tive Time 
# Silver Halide 
Speed Fog Grad. (Seconds) 
______________________________________ 
None 100 0.21 2.7 30 
2 None 140 0.25 2.9 60 
3 0.075 95 0.11 3.2 30 
4 0.075 120 0.12 3.4 60 
______________________________________