Substituted triazolopyrimidines and their use in light-sensitive photographic elements

Photographic element comprising a support and a silver halide emulsion layer comprising in said emulsion layer and/or in a water-permeable layer coated at the same side of the support as said emulsion layer a compound corresponding to the following general formula: ##STR1## wherein: each of R.sup.1, R.sup.2, and R.sup.3, which may be the same or different, can represent hydrogen, C.sub.1 -C.sub.8 alkyl, or Alk.sub.1 - X - Alk.sub.2 - Y -, wherein: Alk.sub.1 is C.sub.1 -C.sub.8 alkyl, which may be substituted, X is --O-- or --S--, Alk.sub.2 is C.sub.1 -C.sub.8 alkylene, which may be substituted, and Y is a single bond, --O--, --S--, --CONH--, --SO.sub.2 NH--, or --NHCONH--, R.sup.3 can alternatively represent C.sub.1 -C.sub.8 alkyl-thio, the C.sub.1 -C.sub.8 alkyl group of which can be substituted, at least one of R.sup.1, R.sup.2, and R.sup.3, however, being other than hydrogen and other than C.sub.1 -C.sub.8 alkyl. The invention disclosed includes compounds per se, which correspond to said general formula.

The present invention relates to improved photographic elements comprising 
light-sensitive silver halide emulsions containing substituted 
triazolopyrimidines. 
It is well known that photographic elements comprising light-sensitive 
gelatin silver halide emulsion layers are subject to fogging. Fogging in 
general and chemical fogging in particular can be defined as the formation 
of a uniform deposit of silver on development. The formation of fog 
depends on many variables such as the nature of the silver halide 
emulsions, their age, the conditions of storage, the development 
conditions, etc. Anyway, fog adversely influences the image quality. The 
formation of fog tends to be more extensive as the time of storage and the 
temperature and relative humidity of the atmosphere in which the emulsions 
are stored, increase. 
Additives to the photographic material known as stabilizers or antifoggants 
protect the light-sensitive silver halide emulsions against formation and 
growth of fog particularly in highly sensitive emulsions and in emulsions 
which are to be stored in conditions of high temperature and humidity as 
exist e.g. in tropical countries. 
It is well known to use compounds of the triazolopyrimidine type 
(azaindolizines) as stabilizers for light-sensitive silver halide 
emulsions. 
It is also known to use certain compounds of the triazolopyrimidine type as 
substitutes for cadmium salts, which have been used successfully in high 
contrast silver halide lith emulsions to improve their sensitivity and 
contrast. Regretfully, cadmium salts are ecologically harmful. 
Several attempts have been made to find modified triazolopyrimidine 
stabilizers, which stabilize light-sensitive silver halide emulsions in 
extreme storage circumstances and at the same time do not decrease their 
sensitivity. For instance the U.S. patent specification No. 2,566,659, the 
Dutch patent application No. 6501053, and the European patent application 
No. 0 096 561 describe the use of thioether-substituted 
triazolopyrimidines in light-sensitive silver halide emulsions to protect 
them against the growth of chemical fog during storage. The U.K. patent 
specification No. 1,203,757 describes the use of iodo-substituted 
triazolopyrimidines and U.K. Patent specification No. 1,209,146 the use of 
amino-substituted triazolopyrimidines for the same purpose. Other modified 
triazolopyrimidines were claimed to have a stabilizing effect on silver 
halide emulsions including lith emulsions. For instance the Japanese 
Patent application No 75-39537 teaches the use of 
isothioureido-substituted triazolopyrimidines and the U.K. Patent 
specification No. 1,500,278 describes the use of 
carboxymethylthio-substituted triazolopyrimidines as substitutes for 
cadmium salts in lith emulsions. 
Nevertheless there is still a need of improving the stabilization of 
light-sensitive silver halide emulsions whilst maintaining their 
sensitivity. 
There also remains a need to provide compounds that replace the 
ecologically harmful cadmium salts formerly used in lith emulsions to 
improve their photographic characteristics, especially their gradation. 
It has now been found that substituted triazolopyrimidines as defined 
hereinafter can be used for these purposes. 
Accordingly the present invention provides a photographic element 
comprising a support and at least one light-sensitive silver halide 
emulsion layer and comprising in said emulsion layer and/or in at least 
one water-permeable hydrophilic colloid layer coated at the same side of 
the support as said emulsion layer at least one 
7-hydroxy-s-triazolo[1,5-a]-pyrimidine compound corresponding to the 
following general formula: 
##STR2## 
wherein: each of R.sup.1, R.sup.2, and R.sup.3, which may be the same or 
different, can represent: 
hydrogen, 
a C.sub.1 -C.sub.8 alkyl group, e.g. methyl, or 
an Alk.sub.1 --X--Alk.sub.2 --Y-- group, wherein 
Alk.sub.1 represents a C.sub.1 -C.sub.8 alkyl group e.g. methyl, ethyl, or 
octyl, or a substituted C.sub.1 -C.sub.8 alkyl group e.g. C.sub.1 -C.sub.8 
Alkylsubstituted with hydroxy, carboxy, acetoxy, phenyl C.sub.1 -C.sub.8 
alkyl-thio such as methylthio or ethylthio, C.sub.1 -C.sub.8 alkyloxy such 
as methoxy, hydroxy-C.sub.1 -C.sub.8 Alkylthio such as 2-hydroxyethylthio, 
or hydroxy-C.sub.1 -C.sub.8 alkyloxy, 
X represents--O-- or --S--, 
Alk.sub.2 represents a C.sub.1 -C.sub.8 alkylene group e.g. methylene or 
ethylene, or a substituted C.sub.1 -C.sub.8 alkylene group e.g. C.sub.1 
-C.sub.8 alkylene substituted with carboxy or carboxymethyl, and 
Y represents a single bond, --O--, --S--, --CONH--, --SO.sub.2 NH--, or 
--NHCONH--, 
R.sup.3 can alternatively represent a C.sub.1 -C.sub.8 alkyl-thio group or 
a C.sub.1 -C.sub.8 Alkyl-thio group, the C.sub.1 -C.sub.8 Alkyl of which 
can be substituted with hydroxy, carboxy, acetoxy, phenyl, C.sub.1 
-C.sub.8 alkylthio, C.sub.1 -C.sub.8 Alkyloxy, hydroxy-C.sub.1 -C.sub.8 
Alkylthio, or hydroxy-C.sub.1 -C.sub.8 alkyloxy, 
at least one of R.sup.1, R.sup.2, and R.sup.3, however, being other than 
hydrogen and other than C.sub.1 -C.sub.8 alkyl. 
It has been established that 7-hydroxy-s-triazolo-[1,5-a ]-pyrimidines 
corresponding to the above general formula are particularly good 
stabilizers and antifoggants for both colour and black-and white 
photographic light-sensitive silver halide emulsions and maintain their 
sensitivity. 
It has also been found that said 7-hydroxy-s-triazolo-[1,5-a ]-pyrimidines 
corresponding to the above general formula improve the photographic 
characteristics of lith emulsions. They actually increase their gradation 
and sharpen the toe of the characteristic curve as is very much desirable 
in the case of lith emulsions. Unlike cadmium salts they do not harm the 
environment and thus are interesting substitutes for these heavy metal 
salts. 
Representatives of said 7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine compounds 
corresponding to the above general formula that can be used in accordance 
with the present invention are listed in the following Table 1, the 
symbols used therein referring to the above general formula. 
TABLE 1 
__________________________________________________________________________ 
Compound 
R.sup.1 R.sup.2 R.sup.3 
__________________________________________________________________________ 
1 CH.sub.2OCH.sub.3 CH.sub.3 H 
2 CH.sub.2SCH.sub.3 CH.sub.3 H 
3 CH.sub.2S(CH.sub.2).sub.7CH.sub.3 
CH.sub.3 H 
4 CH.sub.2SCH.sub.2 COOH 
CH.sub.3 H 
5 CH.sub.2SCH.sub.2 CH.sub.2 OH 
CH.sub.3 H 
6 CH.sub.2SCH.sub.2 CH.sub.2SC.sub.2 H.sub.5 
CH.sub.3 H 
7 CH.sub.2SCH.sub.2 CH.sub.2SCH.sub.2 CH.sub.2 OH 
CH.sub.3 H 
8 CH.sub.2SCH.sub.2C.sub.6 H.sub.5 
CH.sub.3 H 
9 CH.sub.2 CH.sub.2SCH.sub.3 
CH.sub.3 H 
10 SCH.sub.2 CH.sub.2SC.sub.2 H.sub.5 
CH.sub.3 H 
11 SCH.sub.2 CH.sub.2SCH.sub.2 CH.sub.2 OH 
CH.sub.3 H 
12 NHCOCH.sub.2SCH.sub.3 
CH.sub.3 H 
13 NHCOCH.sub.2OCH.sub.3 
CH.sub.3 H 
14 H CH.sub.2OCH.sub.3 H 
15 H CH.sub.2SCH.sub.3 H 
16 H CH.sub.2SCH.sub.2 COOH 
H 
17 H CH.sub.2SCH.sub.2 CH.sub.2 OCOCH.sub.3 
H 
18 H CH.sub.2SCH.sub.2 CH.sub.2 OH 
H 
19 H CH.sub.2SCH.sub.2C.sub.6 H.sub.5 
H 
20 H CH.sub.2SCH.sub.2 CH.sub.2SC.sub.2 H.sub.5 
H 
21 CH.sub.2SCH.sub.3 CH.sub.2SCH.sub.3 H 
22 H CH.sub.3 SCH.sub.2C.sub.6 H.sub.5 
23 H CH.sub.3 SCH.sub.2COOH 
24 H CH.sub.3 SCH.sub.2CH.sub.2 OCOCH.sub.3 
1 
25 H CH.sub.3 SCH.sub.2CH.sub.2 OH 
26 H CH.sub.3 SCH.sub.2CHOHCH.sub.2 OH 
27 H CH.sub.3 SCH.sub.2CH.sub.2SCH.sub.2CH.s 
ub.2 OH 
28 H CH.sub.3 CH.sub.2SCH.sub.3 
29 H CH.sub.3 CH.sub.2SCH.sub.2COOH 
30 H CH.sub.3 CH.sub.2SCH.sub.2CH.sub.2 OH 
31 H CH.sub.3 NHCOCH.sub.2SCH.sub.3 
32 H CH.sub.3 NHCOCH.sub.2SCH.sub.2COOH 
33 H CH.sub.3 
##STR3## 
34 H CH.sub.3 NHCOCH.sub.2OCH.sub.3 
35 H CH.sub.3 NHCOCH.sub.2OCH.sub.2COOH 
__________________________________________________________________________ 
7-Hydroxy-s-triazolo-[1,5-a ]-pyrimidine compounds having the above general 
formula are believed to be new compounds and the present invention also 
includes such compounds per se. 
The 7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine compounds corresponding to the 
above general formula can be prepared by techniques described by G. 
Fischer in Journal fuR Signalaufzeichnungsmaterialien 1, 33-42 (1973). 
They can be prepared by condensation of a .beta.-ketoester or of a 
substituted .beta.-ketoester with a 5-amino-1,2,4-triazole according to 
the following reaction scheme: 
##STR4## 
They can be obtained also by conversion of appropriate substituents such as 
e.g. a mercapto group or an amino group standing on the 2-, 5-, and/or 
6-position of a 7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine ring system into 
the specific R.sup.1, R.sup.2, and/or R.sup.3 substituents of the 
compounds of the invention. 
According to these methods the compounds of the invention can be prepared 
very simply and very economically. 
A description of the synthesis of some of the compounds identified in Table 
1 is given hereinafter by way of example. The synthesis of other compounds 
identified in Table 1 as well as of compounds not identified in Table 1 
but corresponding to the above general formula can easily be derived from 
the syntheses described hereinafter. 
Preparation 1: Compound 1 
An amount of 21.8 g (0.17 mol) of 3-methoxymethyl-5-amino-1,2,4-triazole 
melting at 100.degree. C. and prepared from aminoguanidinium hydrogen 
carbonate and methoxyacetic acid in toluene as described in the U.K. 
patent specification No. 765,728 and 32.5 g (0.28 mol) of methyl 
acetoacetate was refluxed for 4 h in 50 ml of acetic acid. A mixture 
consisting of methanol, water, and acetic acid (25 ml) was distilled off. 
The remaining reaction mixture was stirred with 50 ml of ethanol, filtered 
with suction, and rinsed with ethanol. 
Yield: 11.5 g (35%) of Compound 1. Melting point: &gt;265.degree. C. 
Preparation 2: Compound 2 
Compound 2 was prepared analogously to Compound 1 as described above, but 
from 3-methylthiomethyl-5-amino-1,2,4-triazole melting at 125.degree. C. 
and methyl acetoacetate in acetic acid. 
Yield: (42%). Melting point: 243.degree. C. 
Preparation 3: Compound 4 
(a) 2-Mercaptomethyl-5-methyl-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine was 
prepared by first hydrolysing the corresponding thiouronium salt, as 
described in the U.S. patent specification No. 2,835,581, in boiling 
aqueous sodium hydroxide under nitrogen atmosphere and then acidifying. 
Yield: (75%). Melting point: 215.degree. C. 
(b) A solution of 23.3 g (0.2 mol) of the sodium salt of chloroacetic acid 
in 150 ml of water was added dropwise under nitrogen atmosphere to a 
solution of 39.2 g (0.2 mol) of compound (a), prepared as described above, 
in 80 ml (0.4 mol) of 5 N sodium hydroxide. After having been stirred for 
6 h at room temperature, the reaction mixture was filtered. The filtrate 
was acidified with concentrated hydrochloric acid. The precipitate was 
filtered with suction and rinsed with water and methanol. 
Yield: 37.5 g (74%) of 
2-carboxymethylthiomethyl-5-methyl-7-hydroxy-s-triazolo-[1,5-a 
]-pyrimidine(Compound 4). Melting point: &gt;265.degree. C. 
Preparation 4: Compound 6 
17.4 g (0.08 mol) of 3-[2-(ethylthio)-ethylthiomethyl]-5-amino- 
1,2,4-triazole melting at about 80.degree. C. and 13.9 g (0.12 mol) of 
methyl acetoacetate were refluxed for 4 h in 30 ml of acetic acid. The 
precipitate was filtered with suction and rinsed with ethanol. 
Yield: 13.5 g (59%) of Compound 6. Melting point: about 165.degree. C. 
Preparation 5: Compound 9 
Compound 9 was prepared analogously to Compound 1 as described above, but 
from 3-[2-(methylthio)-ethyl]-5-amino-1,2,4-triazole melting at about 
110.degree. C. and methyl acetoacetate in acetic acid. 
Yield: (69%). Melting point: 222.degree. C. 
Preparation 6: Compound 10 
Compound 10 was prepared analogously to Compound 1. 
Yield: (30%). Melting point: 168.degree. C. 
Preparation 7: Compound 14 
Compound 14 was prepared analogously to Compound 1 as described above, but 
from ethyl 4-methoxyacetoacetate boiling at 55.degree.-60.degree. C./5 mm 
and prepared as described in Journal of Organic Chemistry 43, 2087 (1978). 
Yield: (75%). Melting point: about 265.degree. C. 
Preparation 8: Compound 15 
Compound 15 was prepared analogously to Compound 6 as described above, but 
from 4-(methylthio)acetoacetic acid methyl ester boiling at 
78.degree.-79.degree. C./1.5 mm. 
Yield: (73%). Melting point: 215.degree. C. 
Preparation 9: Compound 17 
Compound 17 was prepared analogously to Compound 1 as described above, but 
from 4-(2-acetoxy-ethyl-thio)acetoacetic acid methyl ester boiling at 
129.degree.-131.degree. C./0.5 mm and prepared by alkylation of 
2-acetoxy-ethanethiol with 4-chloro-acetoacetic acid methyl ester in a 
mixture of toluene and triethylamine. 
Yield: (85%). Melting point: about 120.degree. C. 
Preparation 10: Compound 18 
12.5 ml of concentrated hydrochloric acid was added dropwise to a solution 
of 26.8 g (0.1 mol) of Compound 17 in 100 ml of methanol. The reaction 
mixture was refluxed for 5 h. The precipitate was filtered with suction 
and recrystallized from water. 
Yield: 11.5 g of Compound 18 (51%). Melting point: 199.degree. C. 
Preparation 11: Compound 20 
Compound 20 was prepared analogously to Compound 6 as described above, but 
from 4-[2-(ethylthio)-ethylthio]-acetoacetic acid ethyl ester boiling at 
140.degree.-145.degree. C./1 mm. 
Yield: (25%). Melting point: about 170.degree. C. 
Preparation 12: Compound 21 
15.3 g (0.1 mol) of 3-methylthiomethyl-5-amino-1,2,4-triazole and 16.2 g 
(0.1 mol) of 4-(methylthio)-acetoacetic acid methyl ester in 15 ml of 
acetic acid were refluxed for 24 h. The reaction product was concentrated 
by evaporation and purified by column chromatography. 
Yield: 10 g (39%) of Compound 21. Melting point: 158.degree. C. 
Preparation 13: Compound 24 
Compound 24 was prepared analogously to Compound 1 as described above, but 
from 2-(acetoxy-ethylthio)-acetoacetic acid ethyl ester boiling at 
108.degree.-110.degree. C./0.5 mm and prepared by alkylation of 
2-acetoxy-ethanethiol with 2-chloroacetoacetic acid ethyl ester in a 
mixture of toluene and triethylamine. 
Yield: (77%). Melting point: about 100.degree. C. 
Preparation 14: Compound 25 
Compound 25 was prepared analogously to Compound 18 as described above, but 
from Compound 24 as described above. 
Yield: (67%). Melting point: about 210.degree. C. 
Preparation 15: Compound 30 
15.4 g (0.05 mol)Aof 
5-methyl-6-diethylaminomethyl-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine 
prepared as described in the French patent specification No. 1,555,789 and 
3.9 g (0.05 mol) of 2-mercapto-ethanol in 50 ml of dimethylformamide were 
heated for 16 h at 120.degree. C. After filtration the reaction mixture 
was concentrated by evaporation. The residue was dissolved in 50 ml of 
water and acidified with concentrated hydrochloric acid. The precipitate 
was filtered with suction and rinsed with ethanol. 
Yield: 6.5 g (54%) of Compound 30. Melting point: 170.degree. C. 
Preparation 16: Compound 31 
12.4 g (0.1 mol) of methylthioacetyl chloride was added dropwise to 18.7 g 
(0.1 mol) of the sodium salt of 
5-methyl-6-amino-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine prepared as 
described in Chemical Abstracts 59, 1659e (1963) and 7.9 g (0.1 mol) of 
pyridine in 150 ml of anhydrous dioxan. The precipitate was filtered with 
suction, rinsed with dioxan, and purified by continuous extraction with 
methanol. 
Yield: 10 g (40%) of Compound 31. Melting point: about 230.degree. C. 
It was surprising to find that substituted 7-hydroxy-s-triazolo-[1,5-a 
]-pyrimidines corresponding to the above general formula, when added to 
silver halide emulsions of whatever type, yield unexpectedly improved 
fog-inhibition results without impairing the sensitivity and, when added 
to lith emulsions--even in the absence of cadmium salts--enhance their 
gradation and sharpen the toe portion of their characteristic curve. 
Compounds according to the above general formula, which have a strong 
fog-inhibiting effect, are the following: 
2-methylthiomethyl-5-methyl-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine 
(Compound 2); 
2-carboxymethylthiomethyl-5-methyl-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine 
(Compound 4); 
5-methylthiomethyl-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine (Compound 15); 
5-methyl-6-hydroxyethylthio-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine 
(Compound 25). 
Preferably, the compounds according to the above general formula are 
incorporated into the light-sensitive silver halide emulsion layer of a 
photographic element. The way in which the compounds are added to the 
light-sensitive silver halide emulsions is not critical and the addition 
can be made during any of the different steps of the emulsion preparation. 
For instance they can be added before, during, or after the emulsion has 
been sensitized chemically, preferably just before the coating of the 
emulsion on a suitable support such as e.g. paper, glass or film. 
Instead of being incorporated into the light-sensitive silver halide 
emulsion layer, the novel compounds used in accordance with the invention 
can also be incorporated into another hydrophilic colloid layer of the 
photographic element (e.g. in an antistress or intermediate layer), which 
is in water-permeable relationship with the light-sensitive silver halide 
emulsion layer and coated at the same side of the support as said emulsion 
layer. 
The compounds used in accordance with the present invention can be 
incorporated into any type of photographic element comprising a 
light-sensitive silver halide emulsion layer e.g. a spectrally sensitized 
silver halide emulsion layer, a non-spectrally sensitized silver halide 
emulsion layer, a silver halide emulsion layer of use in diffusion 
transfer reversal processes for the production of silver images, an X-ray 
silver halide emulsion layer, a lith silver halide emulsion layer, or a 
silver halide emulsion layer sensitive to infra-red radiation. They can be 
incorporated into high speed negative photographic elements as well as 
into rather low speed direct-positive elements. Various silver salts can 
be used as the light-sensitive silver salt e.g. silver bromide, silver 
iodide, silver chloride, or mixed silver halides e.g. silver 
chlorobromide, silver chlorobromoiodide, or silver bromoiodide. 
The silver halides are dispersed in the common hydrophilic colloids such as 
gelatin, casein, zein, polyvinyl alcohol, carboxymethylcellulose, alginic 
acid, etc., gelatin being favoured, however. 
The amount of 7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine compounds used in 
accordance with the invention depends on the particular type of silver 
halide emulsion and the desired effect and may vary within very wide 
limits. The optimum amount is best determined by trial for each particular 
type of emulsion. In general, suitable concentrations are between 0.2 
millimol and 30 millimol per mol of silver halide. 
The light-sensitive silver halide emulsions can be sensitized chemically by 
effecting the ripening in the presence of small amounts of compounds 
containing sulphur e.g. allyl thiocyanate, allyl thiourea, sodium 
thiosulphate, etc. The emulsions can be sensitized also by means of 
reductors e.g. tin compounds as described in our U.K. patent specification 
No. 789,823 and small amounts of noble metal compounds e.g. gold, 
platinum, palladium, iridium, ruthenium, and rhodium. 
Other additives such as hardening agents, wetting agents, plasticizers, 
colour couplers, developing agents, and spectral sensitizers can also be 
incorporated into the emulsion in the usual way. 
The compounds according to the general formula can be used advantageously 
in combination with compounds that sensitize the emulsion by development 
acceleration e.g. alkylene oxide polymers. Such alkylene oxide polymers 
can be of various types. Various derivatives of alkylene oxides can be 
used to sensitize the silver halide emulsions e.g. alkylene oxide 
condensation products as described in the U.S. patent specification Nos. 
2,531,832 and 2,533,990, in the U.K. patent specifications Nos. 
920,637--940,051--945,340--991,608, and in Belgian patent specification 
No. 648,710. Other compounds that sensitize the emulsion by development 
acceleration and that are suitable for use in combination with the 
compounds according to the present invention are the onium derivatives of 
amino-N-oxides as described in the Belgian patent specification No. 
686,520. 
The stabilizers defined by the general formula herein can be used in 
combination with known stabilizers such as e.g. heterocyclic nitrogen 
containing thioxo compounds such as benzothiazoline-2-thione and 
1-phenyl-.DELTA.2-tetrazoline-5-thione, with mercury compounds such as 
those described in the Belgian patent specification Nos. 
524,121--677,337--707,386--709,195 and, of course, also in conjunction 
with known compounds of the hydroxytriazolopyrimidine type. 
In lith emulsions one or more compounds corresponding to the above general 
formula can be used alone or in combination with other additives that 
increase the sensitivity. A lith silver halide emulsion comprises at least 
50 mol% of chloride and not more than 5% of iodide, the remainder being 
bromide. Preferably, lith emulsions contain at least 60 mol% of chloride, 
not more than 40 mol% of bromide and not more than 5 mol% of iodide. 
Photographic lith-type elements that may contain compounds corresponding to 
the above general formula can be ortho or pan sensitive or sensitive to 
any other desired spectral region and lith-type elements incorporating 
said compounds can be used for any application for which lith-type 
elements are customarily employed e.g. for the reproduction of continuous 
tone photographs or line drawings for the preparation of printing plates.

In the following examples the effects of some of the compounds 
corresponding to the above general formula in photographic silver halide 
emulsions are illustrated. 
EXAMPLE 1 
A photographic gelatin silver chloride emulsion having an average grain 
diameter of 260 nm was digested in the presence of gold and thiosulphate 
until it reached its maximum speed. The emulsion obtained was divided into 
four portions, to each portion of which 1 millimol of antifoggant as 
listed in Table 2 hereinafter was added per 100 g of silver nitrate. Each 
of the emulsion samples thus obtained was coated on a conventional support 
and dried. 
The freshly prepared samples were developed at 20.degree. C. for 3 min. in 
a developing solution having the following composition : 
______________________________________ 
water 800 ml 
p-monomethylaminophenol sulphate 
1.5 g 
anhydrous sodium sulphite 
50 g 
hydroquinone 6 g 
anhydrous sodium carbonate 
32 g 
potassium bromide 2 g 
water to make 1000 ml 
______________________________________ 
The values of fog and speed are listed also in Table 2. The density (D) 
values given for fog are absolute values. The values of speed were 
measured at density (D) 1.0 above fog. The sample comprising compound A 
was given the speed value 100, the values obtained with the samples 
comprising other compounds being percent values relating to the value of 
the sample containing compound A. 
Compound A is a comparison antifoggant disclosed in Example 1 of the U.S. 
patent specification No. 2,566,659; it carries a methylthio function in 
the 2-position and a methyl group in the 5-position of a 
7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine ring system. 
Compound B is a comparison antifoggant disclosed in the U.K. patent 
specification No. 1,500,278; it carries a carboxymethylthio function in 
the 2-position and a methyl group in the 5-position of a 
7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine ring system. 
TABLE 2 
______________________________________ 
Antifoggant added Fog Speed 
______________________________________ 
Compound A (comparison) 
0.09 100 
Compound B (comparison) 
0.07 85 
Compound 2 0.04 102 
Compound 15 0.03 141 
______________________________________ 
Comparison of the above results shows that the fog-inhibiting effect of the 
compounds 2 and 15 of the invention is manifestly stronger than that of 
the known compounds A and B. It also shows that the speed obtained with 
the compounds 2 and 15 of the invention at least equals, and in fact, 
exceeds the speed obtained with the comparison compounds A and B. 
EXAMPLE 2 
A conventional photographic gelatin silver bromoiodide emulsion (4.5 mol% 
iodide) comprising an amount of silver halide equivalent to 50 g of silver 
nitrate per kg of emulsion was divided into aliquot portions. To all but 
one portion an antifoggant was added in the amounts indicated in Table 3 
hereinafter (in millimol per 50 g of silver nitrate). Each of the emulsion 
samples thus obtained was coated on a conventional support and dried. 
The values of fog and speed of these emulsion samples were determined 
shortly after preparation and again after incubation for 5 days at 
57.degree. C. and 34 percent relative humidity. 
Development occurred at 20.degree. C. for 5 min. in a developing solution 
having the same composition as that described in Example 1. 
The values of fog and speed obtained are listed in Table 3. The density (D) 
values given for fog are absolute values. The values I and II given for 
the speed are relative values, "Speed I" standing for speed values 
measured at density (D) 0.1 above fog and "Speed II" standing for speed 
values measured at density (D) 1.0 above fog. The emulsion sample 
comprising 0.5 millimol of compound C was given a speed value of 100, the 
speed values of the other emulsion samples being percent values relating 
to the value of this reference sample. 
Compound C (comparison compound) is the conventionally used 
5-methyl-7-hydroxy-s-triazolo-[1,5-a ]-pyrimidine. 
Compound B (comparison compound) corresponds with Compound B in Example 1. 
TABLE 3 
______________________________________ 
Incubated 
Concen- Fresh emulsion 
emulsion 
Antifoggant 
tration Speed Speed 
added in millimol 
Fog I II Fog I II 
______________________________________ 
none -- 0.21 126 117 2.29 06 
Compound C 
0.5 0.08 100 100 1.60 21 * 
Compound C 
1.0 0.08 83 95 1.13 54 15 
Compound B 
0.5 0.12 115 126 2.20 07 * 
Compound B 
1.0 0.09 102 123 1.84 20 * 
Compound 4 
0.5 0.06 45 60 0.83 56 25 
Compound 4 
1.0 0.06 29 44 0.42 61 58 
Compound 25 
1.0 0.05 70 66 0.86 110 37 
Compcund 25 
2.0 0.06 58 66 0.43 129 98 
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*In this case Speed II cannot be determined because the fog is too high. 
Comparison of the above results shows that the fog-inhibiting effect of the 
compounds 4 and 25 of the invention is considerably stronger than that of 
the known compounds C and B. It also shows that the speed after incubation 
in the case of the comparison compounds C and B dropped steeply, and in 
general rose slightly in the case of compounds 4 and 25 of the invention, 
thus demonstrating that the addition of the compounds of the invention 
does not result in a reduction of the speed but rather in a stabilization 
thereof. 
EXAMPLE 3 
A lith-type gelatin silver chlorobromoiodide emulsion (8.6 mol% chloride, 
16.0 mol% bromide, and 0.4 mol% iodide) having an average grain diameter 
of 330 nm was digested in the presence of gold, thiosulphate, and 
p-toluene-thiosulphonic acid until it reached its maximum speed. The 
emulsion obtained wad divided into four portions, to each portion of which 
1.0 millimol of compound as listed in Table 4 hereinafter was added per 
100 g of silver nitrate. Each of the emulsion samples thus obtained was 
coated on a conventional support and dried. 
The freshly prepared samples were developed for 1 min 45 s at 27.degree. C. 
in a developing solution comprising 1 part of composition A, 0.5 part of 
composition B, and 2.5 parts of demineralized water: 
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Composition A 
tetrasodium salt of ethylene diamine tetraacetic acid 
4 g 
boric acid 24 g 
anhydrous potassium carbonate 
280 g 
sodium salt of formaldehyde hydrogen sulphite 
200 g 
potassium metabisulphite 15 g 
potassium bromide 8 g 
potassium chloride 24 g 
demineralized water to make 1000 ml 
Composition B 
potassium metabisulphite 2 g 
hydroquinone 60 g 
potassium hydroquinone sulphonate 
40 g 
polyethylene glycol (1000) 1 g 
triethylene glycol 125 ml 
demineralized water to make 500 ml 
______________________________________ 
The values of fog, speed, and gradation are listed in Table 4. The density 
(D) values given for fog are absolute values. The values of speed were 
measured at density (D) 1.30 above fog. The values of gradation are the 
values of gamma between 0.04 and 1.30 of the characteristic curve. (D) 
0.04 corresponds with 5% of dot area upon screen exposure and (D) 1.30 
corresponds with 95% of dot area. 
The sample containing compound B was given the speed value 100, the values 
obtained with the samples containing the other compounds being percent 
values relating to the value of the sample containing compound B. 
Compound B and Compound A (both comparison compounds) are the same as 
Compounds B and A in Example 1. 
TABLE 4 
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Compound added Fog Speed Gradation 
______________________________________ 
Compound B (comparison) 
0.02 100 1.15 
Compound A (comparison) 
0.01 162 1.00 
Compound 15 0.02 282 2.05 
Compound 2 0.02 102 1.34 
______________________________________ 
Comparison of the above results shows that the gradation obtained with a 
lithographic silver halide emulsion comprising the compounds 2 and 15 of 
the invention is higher than that obtained with the known compounds B and 
A.