Preparation of photosensitive silver halide materials with a combination of organic ripening agents

A photosensitive silver halide emulsion is prepared by providing an emulsion containing an anionic acid-substituted and a neutral organic ripening agent and then growing silver halide grains in the emulsion. This combination of organic ripening agents of differing charge types produces a superadditive effect on the growth of silver halide crystals.

FIELD OF THE INVENTION 
The present invention relates to the preparation of photosensitive silver 
halide emulsions and photographic elements with supports bearing such 
emulsions. 
BACKGROUND OF THE INVENTION 
The preparation of photographic emulsions begins with the formulation of a 
dispersion of microcrystals of silver halide in a protective dispersing 
medium. Subsequent to or concurrent with the formation of these 
microcrystals, a silver halide solvent is introduced to permit 
dissolution, recrystallization, and growth of individual silver halide 
particles to a desired crystal (grain) size. This process is known as 
physical ripening and is typically carried out to increase the size of the 
silver halide crystals, because photographic sensitivity increases with 
increasing grain size. A wide variety of chemical substances function as 
solvents for silver halides; many are listed in T. H. James, ed., The 
Theory of the Photographic Process, 4th ed., Macmillan, New York, 1977, p. 
9. Silver halide solvents are also known as Ostwald ripeners, ripening 
agents, crystal growth modifiers, fixing agents, and growth accelerators. 
In addition to enhancing silver halide crystal size, recrystallization 
reactions by ripening agents at apparently fixed crystal dimensions are 
also known to modify silver halide morphology, to alter the concentration 
of crystal defects and to promote the incorporation in the silver halide 
crystal lattice of sensitizing species such as silver or silver sulfide 
clusters. These ripener-induced changes tend to increase the photographic 
sensitivity of silver halide emulsions, and since all these changes 
involve recrystallization phenomena which also participate in silver 
halide growth, these phenomena are included hereafter in the discussion 
and claim regarding silver halide growth. 
Among the substances reported to be effective ripening agents are excess 
halide ion and ammonia, as described in G. F. Duffin, Photographic 
Emulsion Chemistry, Focal Press Ltd., London, 1966, pp. 60-62, and 
thiocyanate ion, as disclosed in U.S. Pat. No. 3,320,069 to Illingsworth. 
Many organic compounds have also been reported to function as ripeners. 
For example, U.S. Pat. Nos. 3,271,157 to McBride and 3,574,628 to Jones 
disclose the use of thioether compounds as ripening agents for silver 
halide photographic materials. U.S. Pat. No. 4,782,013 to Herz et al. 
discloses the use of macrocyclic ether compounds containing oxygen, 
sulfur, and selenium atoms for this purpose. 
Silver halide solvents or ripening agents are generally ligands for 
Ag.sup.+ ions that combine with Ag.sup.+ ions to form soluble Ag.sup.+ 
adducts or complex ions. Although ripening agents are very useful for 
controlling the size, dispersity, and morphology of silver halide grains 
and for determining the location of specific halide components in mixed 
silver halide compositions, they also cause problems in emulsions during 
keeping or storage. Specifically, ripeners that are retained in an 
emulsion after formation and growth of the silver halide grains can change 
the rates of chemical sensitization, interfere with spectral 
sensitization, and promote fog formation during storage of emulsions, 
particularly those coated on a support. 
To avoid these undesirable effects, efforts have been made to remove 
organic ripeners from emulsions after formation and growth of silver 
halide grains by purification procedures such as washing. However these 
ripening agents cannot be completely removed from emulsions even by 
extensive wash procedures, most likely because of their relatively low 
aqueous solubility and their affinity for silver halide. U.S. Pat. No. 
4,665,017 to Mifune et al., proposes to circumvent this difficulty by 
deactivating residual ripeners through an oxidation process. This 
approach, however, has the disadvantage that gelatin in the emulsion also 
undergoes irreversible changes on oxidation. Furthermore, some ripening 
agents, e.g., thiourea compounds, upon oxidation yield products of 
increased activity with respect to desensitization and fog formation. 
Another approach to countering the undesirable effect of residual silver 
halide solvent is the addition of emulsion stabilizers and antifoggants. 
However, such additives tend to interfere with spectral sensitization and 
can lead to loss of emulsion sensitivity. 
Organic silver halide solvents or ripening agents can be classified into 
two types: neutral and acid-substituted. A neutral ripening agent is a 
compound which either is uncharged or carries an equal number of positive 
and negative ionic charges, i.e., a zwitterionic compound. An 
acid-substituted ripening agent is a compound that incorporates a 
covalently bonded acidic function which, upon deprotonation at about pH 7 
or below, confers a negative charge on the molecule. These two classes of 
ripening agents are exemplified by the neutral compound ethanolamine and 
its acid-substituted analog, glycine. Both compounds yield Ag.sup.+ 
complexes of similar stability and are capable of ripening AgBr emulsions. 
However in dilute alkaline solution, where its acidic function is 
deprotonated, glycine dissolves AgBr much more slowly than does the 
neutral ethanolamine (D. Shiao, L. Fortmiller, and A. Herz, J. Phys. 
Chem., 1975, 79, 816). 
Similarly, U.S. Pat. No. 4,749,646 to Herz et al. discloses that 
N,N,N',N'-tetramethylthiourea accelerates silver halide grain growth, as 
measured by equivalent circular diameter, more than its 
N,N'-dicarboxymethyl-N,N'-dimethylsubstituted analog. On the other hand, 
the high level of storage fog induced by tetramethylthiourea is somewhat 
diminished when it is replaced by its N,N'-dicarboxyethyl-N,N'-dimethyl 
analog. 
U.S. Pat. Nos. 4,695,535 to Bryan, et al., and 4,865,965 to Friour et al., 
also disclose acid-substituted ripening agents. The ripeners disclosed in 
U.S. Pat. No. 4,695,535 are acyclic thioether compounds containing carboxy 
substituents; the acid-substituted ripening agents disclosed in U.S. Pat. 
No. 4,865,965 are cyclic ethers. 
The cited art makes it apparent that, when coated under a conventional 
condition at pH values above about 4.6, acid-substituted ripeners 
interfere less with dye sensitization and cause less storage fog than 
their neutral analogs. However, under such pH conditions the 
acid-substituted ripeners exist substantially in their anionic state and 
often suffer from the distinct disadvantage of exhibiting low activities 
as accelerators of silver halide growth. Hence, it is the major purpose of 
the present invention to overcome this barrier for the convenient 
application of acid-substituted ripeners in photographic systems as useful 
promoters of silver halide dissolution, recrystallization and growth by 
using them in combination with a relatively low level of a neutral organic 
ripener. 
SUMMARY OF THE INVENTION 
The present invention relates to the preparation of a photosensitive silver 
halide emulsion and to a photosensitive element with a support bearing 
that emulsion. Such emulsions are prepared by providing an emulsion 
comprising of: 
an anionic acid-substituted organic ripening agent having the general 
formula (I) or (II) 
EQU (A).sub.a R.sup.1 [XR.sup.2 (A).sub.b ].sub.m [YR.sup.3 (A).sub.c 
].sub.n(I) 
##STR1## 
wherein each A is independently a covalently bonded acidic substituent; 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently 
hydrocarbon or fluorocarbon groups having from 1 to 6 carbon atoms, which 
groups are unsubstituted or substituted with one or more neutral 
functional groups containing heteroatoms selected from the group 
consisting of halogen, oxygen, sulfur, and nitrogen; 
X is selected from the group consisting of S, Se, and Te; and 
Y is selected from the group consisting of O, S, Se, and Te; a, b, and c 
are independently 0, 1, or 2, and at least one of a, b, or c is greater 
than zero, 
m and n are independently zero to 6; 
Z is selected from the group consisting of O, S, Se, Te, and --NR.sup.7 
(A).sub.g, wherein R.sup.7 is a lower hydrocarbon group which is 
unsubstituted or substituted as described for R.sup.1, R.sup.2, R.sup.3, 
R.sup.4, R.sup.5, and R.sup.6 ; 
d, e, f, and g are independently 0 or 1, and at least one of d, e, f, and g 
is 1; and 
a neutral organic ripening agent having the general formula (III) or (IV) 
EQU R.sup.1 (XR.sup.2).sub.m (YR.sup.3).sub.n (III) 
##STR2## 
wherein m and n are independently zero to 6; 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently 
hydrocarbon or fluorocarbon groups having from 1 to 6 carbon atoms, which 
groups are unsubstituted or substituted with one or more neutral 
functional groups containing heteroatoms selected from the group 
consisting of halogen, oxygen, sulfur, and nitrogen; 
X is selected from the group consisting of S, Se, and Te; and 
Y is selected from the group consisting of O, S, Se, and Te; and 
Z is selected from the group consisting of O, S, Se, Te, and --NR.sup.7, 
wherein R.sup.7 is a hydrocarbon group which is unsubstituted or 
substituted as described for R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, 
and R.sup.6 ; and growing silver halide grains in the emulsion. 
The combination of anionic acid-substituted and neutral organic ripening 
agents is highly advantageous, because it produces a superadditive effect 
on silver halide grain growth without adversely affecting sensitization or 
inducing fog. 
DETAILED DESCRIPTION OF THE INVENTION 
Photosensitive silver halide emulsions are prepared by a process 
comprising: 
providing an emulsion comprising: 
an anionic acid-substituted organic ripening agent having the general 
formula (I) or (II) 
EQU (A).sub.a R.sup.1 [XR.sup.2 (A).sub.b ].sub.m [YR.sup.3 (A).sub.c 
].sub.n(I) 
##STR3## 
wherein each A is independently a covalently bonded acidic substituent; 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently 
hydrocarbon or fluorocarbon groups having from 1 to 6 carbon atoms, which 
groups are unsubstituted or substituted with one or more neutral 
functional groups containing heteroatoms selected from the group 
consisting of halogen, oxygen, sulfur, and nitrogen; 
X is selected from the group consisting of S, Se, and Te; and 
Y is selected from the group consisting of O, S, Se, and Te; 
a, b, and c are independently 0, 1, or 2, and at least one of a, b, or c is 
greater than zero, 
m and n are independently zero to 6; 
Z is selected from the group consisting of O, S, Se, Te, and --NR.sup.7 
(A).sub.g, wherein R.sup.7 is a lower hydrocarbon group which is 
unsubstituted or substituted as described for R.sup.1, R.sup.2, R.sup.3, 
R.sup.4, R.sup.5, and R.sup.6 ; 
d, e, f, and g are independently 0 or 1, and at least one of d, e, f, and g 
is 1; and 
a neutral organic ripening agent having the general formula (III) or (IV) 
EQU R.sup.1 (XR.sup.2).sub.m (YR.sup.3).sub.n (III) 
##STR4## 
wherein m and n are independently zero to 6; 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently 
hydrocarbon or fluorocarbon groups having from 1 to 6 carbon atoms, which 
groups are unsubstituted or substituted with one or more neutral 
functional groups containing heteroatoms selected from the group 
consisting of halogen, oxygen, sulfur, and nitrogen; 
X is selected from the group consisting of S, Se, and Te; and 
Y is selected from the group consisting of O, S, Se, and Te; and 
Z is selected from the group consisting of O, S, Se, Te, and --NR.sup.7, 
wherein R.sup.7 is a hydrocarbon group which is unsubstituted or 
substituted as described for R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, 
and R.sup.6 ; and 
growing silver halide grains in the emulsion. 
As previously described, an acid-substituted organic ripening agent 
contains a covalently bonded acidic function which, upon deprotonation at 
about pH 7 or below, confers a negative charge on the molecule. Also, as 
previously described, a neutral organic ripening agent is a compound that 
either is uncharged or carries an equal number of positive and negative 
ionic charges. 
The acidic groups on the acid-substituted organic ripeners can, in 
accordance with the present invention, be selected from the group 
consisting of --CONHOH, --OPO(OR')OH, --PO(PR')OH, --COOH, --SO.sub.3 H, 
--SO.sub.2 H, --SeO.sub.3 H, --SeO.sub.2 H, --CH(CN).sub.2, --SH, 
--SO.sub.2 SH, --SeH, --SO.sub.2 SeH, --CONHCOR', --CONHSO.sub.2 R', 
--SO.sub.2 NHSO.sub.2 R', and --CR'.dbd.NOH, where R' is H or a lower 
alkyl or aryl group. 
The R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 substituents 
on the ripening agents are each independently hydrocarbon or fluorocarbon 
groups having from 1 to 6 carbon atoms, which groups are unsubstituted or 
substituted with one or more neutral functional groups containing 
heteroatoms selected from the group consisting of halogens, oxygen, 
sulfur, and nitrogen. Particularly useful functional groups are 
independently selected from the group consisting of --OH, --COR.sup.9, 
--OR.sup.9, --CONHR.sup.9, --SONHR.sup.9, and --SO.sub.2 R.sup.9, where 
R.sup.9 is a lower hydrocarbon group that is unsubstituted or substituted 
as described for R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6. 
R.sup.1 can be linked with R.sup.2 or R.sup.3 to form a cyclic group 
having fewer than 36 ring atoms. R.sup.2 can contain one or more divalent 
groups or atoms selected from the group consisting of --CO--, --O--, 
--CONR.sup.8 --, --S(O)--, --S(O.sub.2)--, --SO.sub.2 NR.sup.8 --, where 
R.sup.8 is a lower hydrocarbon group that is substituted or unsubstituted 
as described for R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6. 
R.sup.4 and R.sup.6, or R.sup.4 and R.sup.5, can be linked to form a 5- or 
6-membered ring, such as an azole, imidazolidine, thiazolidine, 
thiazoline, or morpholine. 
The Ag.sup.+ binding sites contained in acid-substituted and neutral 
organic ripening agents, or ripeners, are not particularly limited. 
Preferred sites are atoms in Group V of the Periodic Table, preferably 
nitrogen or phosphorus compounds exemplified by amines and phosphines, and 
atoms in Group VI, in particular, sulfur, selenium, and tellurium. 
Acid-substituted and neutral organic ripeners that are particularly useful 
for the practice of the present invention belong to the class of ether 
compounds. This class includes the thioethers of the previously-mentioned 
U.S. Pat. Nos. 3,271,157, 3,574,628, and 4,695,535 and the macrocyclic 
ethers of the previously-mentioned U.S. Pat. Nos. 4,782,013 and 4,865,965, 
the thioethers of U.S. Pat. No. 4,695,534 to Bryan et al., the 
selenoethers of U.S. Pat. No. 5,028,522 to Kojima et al., and the thio-, 
seleno-, and telluro-ether compounds disclosed in U.S. Pat. No. 5,004,679 
to Mifune et al., all of which are hereby incorporated by reference. Also 
included for the practice of this invention are the neutral and 
acid-substituted cyclic and acyclic thionamides and their selenium analogs 
as exemplified by the thiourea compounds of U.S. Pat. No. 4,221,863. 
Japanese Public Disclosure 82408/1978 and the previously-mentioned U.S. 
Pat. No. 4,749,646 as well as the Japanese Patent Application Open to 
Public Inspection (OPI) Nos. 144319/78, 82408/78 and 77737/80. Further 
included for the practice of this invention are the thionamides of U.S. 
Pat. Nos. 3,536,487 to Graham, and 3,598,598 to Herz and of British Patent 
Specifications 1,586,412 to Fuji. Other useful ripening agents are thiols 
(mercaptans) such as the compounds of Japanese Patent Application (OPI) 
No. 202531/82 and their selenol analogs. Similarly useful for practicing 
this invention are the ripeners and silver halide solvents belonging to 
the class of triazolium thiolates; this class of compounds is discussed in 
U.S. Pat. No. 4,378,424 to H. Altland et al.; U.S. Pat. No. 4,631,253 to 
H. Mifune et al.; U.S. Pat. No. 4,675,276 to K. Nakamura et al. All these 
various types and classes of compounds are hereby incorporated by 
reference. The acid group of the acid-substituted organic ripening agents 
should have a pka of about 1 to about 8, preferably about 3 to about 6. 
The acid-substituted and neutral organic ripeners can, in accordance with 
the invention, be used at any pH below about pH 13, but, preferably, in 
the range between about 4.6 and 7. The silver halide grains of the 
emulsion can be modified at temperatures between about 30.degree. to about 
90.degree. C., preferably between about 35.degree. to about 70.degree. C. 
Also, in accordance with the present invention, the concentration of 
silver halide in the emulsion can be from 10.sup.-5 to 5 mole/liter, 
preferably from 10.sup.-3 to 2 mole/liter. The concentration of 
acid-substituted organic ripening agent can be from 10.sup.-6 to 10.sup.-1 
mole/mole of silver halide, preferably from 10.sup.-4 to 10.sup.-2 
mole/mole of silver halide. The concentration of neutral organic ripening 
agent can be from 0.01 to 2.5 mole/mole of acid-substituted organic 
ripening agent, preferably from 0.05 to 0.5 mole/mole of acid-substituted 
organic ripening agent. 
Specific examples of acid-substituted and neutral organic ripeners that can 
be used in the present invention are given in Tables I and II, 
respectively. 
TABLE I 
__________________________________________________________________________ 
Acid-Substituted Silver Halide Solvents and Ripeners 
Compound 
Structure 
__________________________________________________________________________ 
A1 H.sub.2 NCH.sub.2 COOH 
A2 4,5-dicarboxyimidazole 
A3 tri(carboxyethyl)phosphine 
A4 m-sulfophenyldimethylphosphine 
A5 Te(CH.sub.2 COOH).sub.2 
A6 Te(CH.sub.2 CH.sub.2 COOH).sub.2 
A7 HOCH.sub.2 CH.sub.2 TeCH.sub.2 CH.sub.2 SO.sub.3 H 
A8 CH.sub.2 (CH.sub.2 TeCH.sub.2 CH.sub.2 CH.sub.2 TeCH.sub.2 
COOH).sub.2 
A9 (CH.sub.2 OCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 COOH).sub.2 
A10 (CH.sub.2 SCH.sub.2 COOH).sub.2 
A11 S(CH.sub.2 CH.sub.2 SCH.sub.2 COOH).sub.2 
A12 (CH.sub.2 SCH.sub.2 CH.sub.2 SCH.sub.2 COOH).sub.2 
A13 O(CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 SCH.sub.2 
CH.sub.2 COOH).sub.2 
A14 (CH.sub.2 OCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 
COOH).sub.2 
A15 O(CH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 COOH).sub.2 
A16 1,10-dithia-4,7,13,16-tetraoxacyclooctadecane-5-carboxylic acid 
A17 1,10-dithia-4,7,13,16-tetraoxacyclooctadecane-5- 
methyleneoxyacetic acid 
A18 [HOOC(CH.sub.2).sub.3 ]N(CH.sub.3)CSN(CH.sub.3)[(CH.sub.2).sub.3 
COOH] 
A19 
##STR5## 
A20 
##STR6## 
A21 
##STR7## 
A22 
##STR8## 
A23 1,10-diselena-4,7,13,16-tetraoxacyclooctadecane-5- 
carboxylic acid 
A24 (CH.sub.2 OCH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 COOH).sub.2 
A25 (CH.sub.2 OCH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 CONHCH.sub.2 
COOH).sub.2 
A26 (CH.sub.2 CH.sub.2 SOCH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 
COOH).sub.2 
A27 (CH.sub.2 OCH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 CH.sub.2 COOH).sub 
.2 
A28 O(CH.sub.2 CH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 COOH).sub.2 
A29 O(CH.sub.2 CH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 CH.sub.2 SeCH.sub. 
2 CH.sub.2 COOH).sub.2 
A30 
##STR9## 
A31 
##STR10## 
A32 
##STR11## 
__________________________________________________________________________ 
TABLE II 
______________________________________ 
Neutral Silver Halide Solvents and Ripeners 
Compound Structure 
______________________________________ 
N1 (CH.sub.2 SCH.sub.2 OH).sub.2 
N2 (CH.sub.2 OCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 OH).sub.2 
N3 (CH.sub.2 OCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 OCH.sub.3).sub. 
2 
N4 Te(CH.sub.2 CH.sub.2 OH).sub.2 
N5 CH.sub.2 (CH.sub.2 TeCH.sub.2 CH.sub.2 OH).sub.2 
N6 (CH.sub.2 OCH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 CH.sub.2 
OH).sub.2 
N7 Ethanolamine 
N8 Pyridine 
N9 H.sub.2 NCOCH(CH.sub.2 OCH.sub.2 CH.sub.2 NH.sub.2).sub.2 
N10 P(CH.sub.2 CH.sub.2 CN).sub.3 
N11 (CH.sub.2 OCH.sub.2 CH.sub.2 SeCH.sub.2 CH.sub.2 CONHEt).sub.2 
N12 1,10-dithia-4,7,13,16-tetraoxacyclooctadecane 
N13 1,7-dithia-4,10,13,16-tetraoxacyclooctadecane 
N14 1,10-diselena-4,7,13,16-tetraoxacyclooctadecane 
N15 Me.sub.2 NCSNMe.sub.2 
N16 Me.sub.2 NCSeNMe.sub.2 
N17 
##STR12## 
N18 
##STR13## 
N19 
##STR14## 
N20 
##STR15## 
N21 
##STR16## 
______________________________________ 
In accordance with the present invention, the combination of 
acid-substituted and neutral organic ripening agents can be added to a 
solution of the dispersion medium, e.g., gelatin, at any stage before, 
during or after formation and chemical or physical ripening of the silver 
halide emulsion. These ripeners can be added simultaneously or singly in 
any order. The procedure for growing silver halide grains with the 
combination of acid-substituted and neutral organic ripeners can be 
accomplished by any of the processes generally known in the art and can be 
achieved at any step of emulsion formation, preparation and sensitization. 
That process includes growth of silver halide emulsions which were formed 
in the absence of any ripener where, after completion of silver halide 
formation, the ripener combination is added to the emulsion which, 
optionally, may contain other additives such as sensitizers of the 
spectral or chemical type, or growth-modifying agents such as azaindenes 
or thiol compounds, or a combination of organic or inorganic ripeners in 
addition to the acid-substituted ripeners of this invention. Also included 
are the art-recognized single jet and multi-jet procedures for silver 
halide formation; among the latter, the double jet technique is preferred 
and the ripener combination, singly or jointly, can be introduced at any 
stage when this technique is used. 
The silver halide emulsions grown and sensitized by the process of the 
present invention can be silver chlorides, silver iodides or silver 
bromides of any crystal habit or shape, including tabular and needle 
forms. The silver halides can also consist of mixed halide compositions, 
e.g. bromoiodides or chloride-rich compositions containing at least 50 
mole % silver chloride. In mixed halide compositions, the various silver 
halides can be randomly distributed throughout the crystal or their 
location can be specified, for example, an emulsion having a silver 
chloride core and an 8 mole % silver bromide shell with a surface layer of 
silver iodide not exceeding 1 mole %. The process of the present invention 
can be carried out at any suitable temperature at pH values ranging 
between about pH 1 to about pH 8, the preferred range being between about 
pH 4.6 and about pH 7; particularly preferred pH values fall in the range 
between about pH 5.3 and pH 6.7. The formation and growth of the silver 
halide emulsion according to this invention can be accomplished with 
either excess silver ions or excess halide ions, but the preferred 
condition for growth involves 0 to about 500 mM excess halide ions, 
preferably between about 0.001 and 50 mM excess halide. Emulsion 
purification procedures before coating are optional, and gelatin is the 
preferred colloid and vehicle for the photosensitive silver halide 
emulsion of the present invention. Other vehicles are disclosed in Section 
IX of Research Disclosure, Item 308119, December 1989, hereinafter 
referred to as Research Disclosure, hereby incorporated by reference. 
The emulsions of the present invention can contain ionic antifogging agents 
and stabilizers such as thiols, thiazolium compounds, exemplified by 
benzothiazolium salts and their selenium and tellurium analogs, 
thiosulfonate salts, azaindenes and azoles. Also included among these 
antifoggants and stabilizers are compound classes which, depending on 
their substituents, can either be ionic or non-ionic; these classes 
include disulfides, diselenides and thionamides. Also specifically 
included are non-ionic antifoggants and stabilizers such as the 
hydroxycarboxylic acid derivatives of W. Humphlett in U.S. Pat. No. 
3,396,028 and the polyhydroxyalkyl compounds of U.S. patent application 
Ser. No. 493,598, entitled "Stabilization of Photographic Recording 
Materials" to Lok and Herz. 
The emulsions of the present invention can contain chemical sensitizers 
such as those based on sulfur, selenium, silver or gold, or combinations 
of such sensitizers. Other sensitizing agents are disclosed in Section III 
of Research Disclosure, hereby incorporated by reference. 
The photographic emulsions of the present invention can be spectrally 
sensitized with dyes such as cyanines, merocyanines, or other dyes shown 
in Section IV of Research Disclosure, hereby incorporated by reference. 
The photographic emulsions of the present invention can contain color image 
forming couplers, i.e., compounds capable of reacting with an oxidation 
product of a primary amine color developing agent to form a dye. They can 
also contain colored couplers for color correction or development 
inhibitor-releasing (DIR) couplers. Suitable couplers for the practice of 
the present invention are disclosed in Section VII of Research Disclosure, 
hereby incorporated by reference. 
The photographic emulsions of the invention can be coated on various 
supports, preferably flexible polymeric films. Other supports are set 
forth in Section XVII of Research Disclosure, hereby incorporated by 
reference. 
Emulsions of the present invention can be applied to a multilayer 
multicolor photographic material comprising a support on which is coated 
at least two layers having different spectral sensitivities. Such 
multilayer multicolor photographic materials usually contain at least one 
red-sensitive emulsion layer, at least one green-sensitive emulsion layer, 
and at least one blue-sensitive emulsion layer. The order of these layers 
can be optionally selected as desired. Usually a cyan-forming coupler is 
associated with the red-sensitive layer, a magenta-forming coupler is 
associated with the green-sensitive layer, and a yellow-forming coupler is 
associated with the blue-sensitive layer. 
The photographic emulsions of the present invention can be processed with 
black and white developing agents such as hydroquinones, 3-pyrazolidones, 
or other compounds such as those disclosed in Section XX of Research 
Disclosure, hereby incorporated by reference. Primary aromatic amine color 
developing agents (e.g., 4-amino-N-ethyl-N-hydroxyethylaniline or 
3-methyl-4-amino-N,N-diethylaniline) can also be employed. Other suitable 
color developing agents are described in L. F. A. Mason, Photographic 
Processing Chemistry, Focal Press, 1966, pp. 226-229, and in U.S. Pat. 
Nos. 2,193,015 and 2,592,364. 
Photographic emulsions of the present invention can be applied to many 
different silver halide photographic materials such as, high speed black 
and white films, X-ray films, and multilayer color negative films, 
including those having diffusion transfer applications. 
As demonstrated by the following examples, the combination of an 
acid-substituted organic ripening agent and a neutral ripening agent in 
accordance with the present invention achieves a superadditive effect on 
silver halide growth, an effect which is not obtained by a combination of 
ripeners belonging to the same charge type. In addition, the combination 
of acid-substituted and neutral organic ripening agents of the present 
invention requires no subsequent removal or deactivation of these agents, 
because they cause no deleterious effects such as, desensitization or fog 
formation during subsequent sensitizing of the emulsion, or during its 
storage and coating.

EXAMPLES 
EXAMPLE 1 
Ostwald ripening rates of small-particle silver halide emulsions were 
determined using Rayleigh light scatter measurements. Details of the 
measurement method are disclosed in A. L. Smith, ed., Particle Growth in 
Suspensions, Academic Press, London, 1973, pp. 159-178. At a temperature 
of 25.degree. C. and a pH of 6, 8 mM AgBr emulsions of about 50 nm initial 
diameter dispersed in 0.1% ossein gelatin (isoelectric point 4.9) 
containing 30 volume percent methanol and 20-28 mM KNO.sub.3 in 1 mM KBr 
(pBr 3) were mixed with varying amounts of the neutral and 
acid-substituted ripening agents of Tables I and II. Turbidity changes as 
a function of time, which corresponded to AgBr growth rates, were measured 
at 436 nm. Growth rates were normalized with respect to the rate obtained 
in the absence of an added organic ripening agent; measurements were 
reproducible within 15%. The following results were obtained: 
______________________________________ 
Test Ripener (conc. in mM) 
Relative AgBr Growth Rate 
______________________________________ 
1 N1 (0.01) 1.3 
2 N1 (0.05) 4.7 
3 A10 (0.1) 1.2 
4 A10 (3.0) 2.1 
5 N12 (0.01) 1.9 
6 A16 (0.01) 1.1 
7 A18 (0.3) 1.8 
______________________________________ 
Comparing the results for A10 with those of the results for N1, and the 
results for A16 with those of N12 demonstrates that under the test 
conditions an acid-substituted ripening agent was a less active AgBr 
growth accelerator than its neutral analog and thus required a higher 
concentration than the latter to exhibit similar activity. The 
acid-substituted thiourea A18 also showed relatively weak ripening 
activity under the test conditions. 
Next, the AgBr growth rates, produced by combinations of ripeners, were 
determined by the above-described method. If there was no interaction 
between the ripeners themselves, the observed growth rate from the 
combination of ripeners would be the product of the rates observed for the 
individual compounds. Thus, for example, the relative rate for a 
combination of 0.01 mM A16 and 0.3 mM A18 calculated from the foregoing 
results of Tests 6 and 7 would be 1.1.times.1.8, or 2.0. An observed rate 
lower than that calculated would indicate an antagonistic effect between 
the ripeners. An observed rate higher than that calculated, on the other 
hand, would indicate a synergistic, superadditive effect between them. 
The following are the calculated and observed relative AgBr growth rates 
for several combinations of ripeners: 
______________________________________ 
Relative AgBr Growth 
Ripener Combination 
Rates Obs./ 
Test (conc. in mM) Observed Calculated 
Calc. 
______________________________________ 
8 A18 (0.3) + A16 (0.01) 
2.1 2.0 .about.1 
9 A18 (0.3) + N12 (0.01) 
4.8 3.4 1.4 
10 A18 (0.3) + A10 (0.10) 
1.8 2.2 0.86 
11 A18 (0.3) + N1 (0.05) 
15 8.5 1.8 
12 A10 (3.0) + A16 (0.01) 
2.4 2.3 .about.1 
13 A10 (3.0) + N12 (0.01) 
4.9 4.0 1.2 
14 A10 (3.0) + N1 (0.05) 
35 9.9 3.5 
______________________________________ 
The observed relative AgBr growth rate for the combination of the 
acid-substituted ripeners A18 and A16 (Test 8) was 2.1 which was very 
close to the value of 2.0 calculated above. Similarly, the observed rate 
for the combination of A10 and A16 (Test 12) was 2.4 which was nearly the 
same as the calculated value of 2.3. The combination of A18 and A10 (Test 
10), however, yielded an observed rate that suggested a slight 
interference between the ripeners. 
When the acid-substituted ripener A18 was combined with either of the 
neutral ripeners N12 or N1 (Tests 9 and 11), the observed growth rates 
were greater than those calculated by factors of 1.4 and 1.8, 
respectively, demonstrating a significant superadditive effect. Similarly, 
the acid-substituted A10 in combination with either of the neutral 
ripeners N12 or N1 (Tests 13 and 14) exhibited superadditivity with an 
observed/calculated growth rate of 3.5 for the A10-N1 combination. These 
results demonstrate the advantageous ripening activity of a combination of 
an acid-substituted organic ripening agent and a neutral organic ripening 
agent in accordance with the present invention. 
EXAMPLE 2 
Aliquots of a AgBr emulsion, as described in Example 1, were mixed with 
various ripening agents and ripened at 25.degree. C., pH 6.8, and pBr 3 
for 5 hours. The reactions were then quenched by the addition of 
N-ethyl-N'-sulfobutyl-9-methylthiacarbocyanine. The resulting AgBr 
crystals were determined by electronmicrography with the crystal sizes 
being expressed as equivalent circular diameters (ECD) in .mu.m. The 
results were as follows: 
______________________________________ 
AgBr Crystal Size 
Test Ripener(s) (conc. in mM) 
EDC, .mu.m 
______________________________________ 
1 None 0.023 
2 N11 (0.02) 0.048 
3 A24 (0.10) 0.047 
4 A24 (0.12) 0.067 
5 A24 (0.10) + N11 (0.02) 
0.27 
______________________________________ 
As shown in Test 2, the neutral ripener N11 at a concentration of 0.02 mM 
produced an approximate doubling of the AgBr crystal size compared with 
the noripener condition (Test 1). A concentration of 0.10 mM of the 
acid-substituted ripener A24 (Test 3) was required to achieve a similar 
result. The combination of 0.10 mM A24 and 0.02 mM N11 (Test 5), however, 
produced a greater than 10-fold increase in crystal size, demonstrating 
the remarkable advantage of combining an acid-substituted and a neutral 
organic ripening agent in accordance with the present invention. 
EXAMPLE 3 
Clearing time, defined as the time required for disappearance of the last 
visible traces of silver halide, was determined for a hardened AgBr 
emulsion coating containing 15.5 mg/dm.sup.2 Ag. The technique employed 
was "split field visual photometry," in which strips of the emulsion 
coating on a transparent support were partially immersed in 0.5M aqueous 
sodium hydroxide containing 0.1 mM of the acid-substituted ripening agent 
A2 and varying amounts of other ripening agents. After all the silver 
halide had been removed from the immersed portion of the strip, the entire 
strip was immersed in the alkaline solution and agitated until the 
demarcation line formed by the initial partial immersion of the strip was 
no longer visually detectable. The clearing times at 25.degree. C. thus 
determined for the various combination of silver halide solvents (ripening 
agents) were normalized with respect to the clearing time measured for the 
solution containing A2 as the only ripening agent. The test results, 
expressed as relative rates of emulsion clearing and reproducible within 
.+-.30%, were as follows: 
______________________________________ 
Additional Ripener* 
Relative Emulsion 
Test (conc. in mM) Clearing Rate 
______________________________________ 
1 Al (0.064) 1 
2 N7 (0.064) 2.6 
3 N15 (0.0064) 5.2 
4 A10 (0.0064) 1 
5 N1 (0.0064) 4.8 
6 N12 (0.0064) 8.2 
______________________________________ 
*In addition to 0.1 mM A2 present in all solutions. 
Addition of a second acid-substituted ripener such as A1 or A10 (Tests 1 
and 4, respectively) produced no change in emulsion clearing rate relative 
to that obtained with A2 alone. However, addition of the neutral ripener 
N7 at a concentration of 0.064 (Test 2) increased the clearing rate by a 
factor of 2.6. Approximately five-fold rate enhancements were obtained 
with added N15 and N1 (Tests 3 and 5, respectively), even at the low 
concentration of 0.0064 mM. An even greater benefit was obtained with 
0.0064 mM N12 (Test 6), which increased the relative clearing rate by a 
factor of 8.2. These results again demonstrate the advantageous results 
obtained from the combination of an acid-substituted and a neutral organic 
ripening agent in accordance with the present invention. 
EXAMPLE 4 
Ripening rates of a small-particle AgBr emulsion were determined, as 
described in Example 1, using the acid-substituted ripening agent A14 and 
the neutral ripening agent N12 singly and in combination. The following 
results were obtained: 
______________________________________ 
Relative AgBr 
Growth Rates Obs./ 
Test Ripener(s) (conc. in mM) 
Observed Calculated 
Calc. 
______________________________________ 
1 A14 (0.06) 5.6 
2 N12 (0.01) 1.8 
3 A14 (0.06) + N12 (0.01) 
157 10.1 15.5 
______________________________________ 
From the growth rates observed with A14 and N12 alone (Tests 1 and 2, 
respectively), a relative growth rate of 10.1 was calculated for their use 
in combination. However the growth rate actually observed from the 
combination of 0.06 mM A14 and 0.01 mM N12 in accordance with the present 
invention was 157, a greater than 15-fold superadditivity enhancement. 
Although the invention has been described in detail for the purpose of 
illustration, it is understood that such detail is solely for that 
purpose, and variations can be made therein by those skilled in the art 
without departing from the spirit and scope of the invention which is 
defined by the following claims.