ALKALINE PROCESSING COMPOSITION CONTAINING A SOLUBLE SILVER COMPLEX FORMED FROM A DIFUNCTIONAL COMPOUND CONTAINING A-S-MOIETY

PRODUIT DE TRAITEMENT ALCALIN CONTENANT UN COMPLEXE SOLUBLE D'ARGENT DE TYPE COMPOSE DIFONCTIONNEL, DONT L'UNE DES PARTIES CONTIENT UN S

English Abstract

Abstract of the Disclosure
Difunctional compounds wherein one of said
functions is a hard or soft atom that ionizes to the
corresponding anion in alkaline solution to combine with
silver cation and the other of said functions is a non-
ionizable soft base that additionally combines with said
silver cation are employed as silver halids complexing
agents in photography. In a preferred embodiment, the
difunctional compound possesses (a) an O, N or C atom that
ionizes to the corresponding O?, N? or C? anion in basic
solution and (b) and -S- containing moiety excluding -SH and
moieties that from -SH in basic solution wherein the -S- of
said moiety is positioned alpha, beta, gamma, delta, epsilon
or zeta to said anion.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A photographic processing composition comprising an aqueous
alkaline processing solution including therein a silver halide solvent which
forms a silver complex soluble in said aqueous alkaline solution, said silver
halide solvent being a difunctional compound wherein one of said functions is
a hard or soft atom that ionizes to the corresponding anion in said alkaline
solution to combine with silver cation and the other of said functions is a
non-ionizable solf base that additionally combines with said silver cation,
wherein difunctional compound possesses (a) an O, N or C atom that ionizes to
the corresponding O?, N? or C? anion in said alkaline solution and (b) an
-S- containing moiety excluding -SH and moieties that form -SH in alkaline
solution, said -S- of said moiety positioned alpha, beta, gamma, delta,
epsilon or zeta to said anion.
2. A photographic processing composition comprising an aqueous
alkaline processing solution including as a silver halide solvent, a compound
of the formula M-(X)n-T wherein M represents an aliphatic or aromatic molecule,
Y-A, wherein A is an atom selected from O, N and C ionizable in said alkaline
solution to the corresponding O?, N? and C? anion and Y represents the
residue of said molecule; T is R-S- or <IMG> wherein R is a monovalent
hydrocarbon radical and R' represents the carbon atoms necessary to complete an
-40-

aromatic or aliphatic ring; X represents a carbon atom;
and n is a whole number from O to 5, said -S- of said R-S-
and <IMG> moieties being positioned alpha, beta,
gamma, delta, epsilon or zeta to said anion.
3. A photographic processing composition as
defined in claim 2 wherein said M represents a 2-amino-4-
hydroxy-1,3,5-triazine.
4. A photographic processing composition as
defined in claim 2 wherein said M represents a 1,2,3,4-
tetrazole.
5. A photographic processing composition as
defined in claim 2 wherein said M represents a
5-pyrazolone.
6. A photographic processing composition as
defined in claim 2 wherein said M represents a 1,2-
disulfonylalkane.
7. A photographic processing composition as
defined in claim 2 wherein said M represents a sulfonamido
derivative of an amino acid.
8. A photographic processing composition as
defined in claim 2 wherein said M represents a 2,4-
dihydroxypyrimidine.
9. A photographic processing composition as
defined in claim 2 wherein said M represents a 4,6-
dihydroxypyrimidine.
10. A photographic processing composition as
defined in claim 2 wherein said T is R-S-.
11. A photographic processing composition as
defined in claim 2 wherein said T is <IMG> .
-41-

12. A photographic processing composition as
defined in claim 10 wherein R is alkyl.
13. A photographic processing composition as
defined in claim 11 wherein R represents the carbon atoms
to complete 2-thienyl.
14. A photographic processing composition as
defined in claim 2 which additionally includes a viscosity-
imparting reagent.
15. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG> .
16. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG> .
17. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG> .
18. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG> .
-42-

19. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG>
20. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG>
21. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG>
22. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG>
23. A photographic processing composition as
defined in claim 2 wherein said silver halide solvent is
<IMG>
-43-

24. A photographic process for forming a water-soluble complex
silver salt with the unexposed and undeveloped silver halide of a photo-
sensitive element which comprises contacting said silver halide with an
aqueous alkaline processing solution including therein a silver halide solvent
which forms a silver complex soluble in said aqueous alkaline solution, said
silver halide solvent being a difunctional compound wherein one of said
functions is a hard or soft atom that ionizes to the corresponding anion in
said alkaline solution to combine with silver cation and the other of said
functions is a non-ionizable soft base that additionally combines with said
silver cation, wherein said difunctional compound possesses (a) an O, N or C
atom that ionizes to the corresponding O?, N? or C ? anion in said alkaline
solution and (b) an -S- containing moiety excluding -SH and moieties that
form -SH in alkaline solution, said -S- of said moiety positioned alpha, beta,
gamma, delta, epsilon or zeta to said anion.
25. A photographic process for forming a water-soluble complex
silver salt with the unexposed and undeveloped silver halide of an exposed
photosensitive element which comprises contacting said silver halide with an
aqueous alkaline processing solution including as a silver halide solvent, a
compound of the formula M-(X)n-T wherein M represents an aliphatic or
aromatic molecule, Y-A, wherein A is an atom selected from 0, N and C ion-
izable in said alkaline solution to the corresponding O?, N? and C? anion
and Y represents the residue of said molecule; T is R-S- or
-44-

<IMG> wherein R is a monovalent hydrocarbon radical and
R' represents the carbon atoms necessary to complete an
aromatic or aliphatic ring; X represents a carbon atom; and
n is a whole number from O to 5, said -S- of said R-S- and
<IMG> moieties being positioned alpha, beta, gamma, delta,
epsion or zeta to said anion.
26. A photographic process as defined in claim 25
wherein said M represents a 2-amino-4-hydroxy-1,3,5-triazine.
27. A photographic process as defined in claim 25
wherein said M represents a 1,2,3,4-tetrazole.
28. A photographic process as defined in claim 25
wherein said M represents a 5-pyrazolone.
29. A photographic process as defined in claim 25
wherein said M represents a 1,2-disulfonylalkane.
30. A photographic process as defined in claim 25
wherein said M represents a sulfonamido derivative of an
amino acid.
31. A photographic process as defined in claim 25
wherein said M represents a 2,4-dihydroxypyrimidine.
32. A photographic process as defined in claim 25
wherein said M represents a 4,6-dihydroxypyrimidine.
33. A photographic process as defined in claim 25
wherein said T is R-S-.
34. A photographic process as defined in claim 25
wherein said T is <IMG>
35. A photographic process as defined in claim 33
wherein R is alkyl.
-45-

36. A photographic process as defined in claim 34
wherein R' represents the carbon atoms to complete 2-thienyl.
37. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG>
38. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG>
39. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG>
40. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG>
41. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG>
-46-

42. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG> .
43. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG> .
44. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG> .
45. A photographic process as defined in claim 25
wherein said silver halide solvent is
<IMG>
46. A photographic process comprising the steps of
(1) developing exposed silver halide of an exposed
photosensitive emulsion with a silver halide developing agent
in aqueous alkaline solution;
-47-

(2) reacting unreduced silver halide of said photosensitive
emulsion with a silver halide solvent which forms a silver complex soluble
in said aqueous alkaline solution, said silver halide solvent being a di-
functional compound wherein one of said functions is a hard or soft atom
that ionizes to the corresponding anion in said alkaline solution to combine
with silver cation and the other of said functions is a non-ionizable soft
base that additionally combines with said silver cation;
(3) transferring said complex silver salt to a superposed
image-receiving layer; and
(4) reducing said transferred complex silver salt to provide
a silver image,
wherein said difunctional compound possesses (a) an 0, N or C atom that
ionizes to the corresponding O?, N? or C? anion in said alkaline solution
and (b) an -S- containing moiety excluding -SH and moieties that form -SH
in alkaline solution, said -S- of said moiety positioned alpha, beta, gamma,
delta, epsilon or zeta to said anion.
47. A photographic process comprising the steps of
(1) developing exposed silver halide of an exposed photosensit-
ive emulsion with a silver halide developing agent in aqueous alkaline
solution;
(2) reacting unreduced silver halide of said photosensitive
emulsion with a silver halide solvent which forms a silver complex soluble in
said aqueous alkaline solution, said silver halide solvent being a compound of
the formula M-(X)n-T wherein M represents an aliphatic or aromatic molecule,
Y-A,
-48-

wherein A is an atom selected from O, N and C ionizable in said
alkaline solution to the corresponding O? , N? and C? anion
and Y represents -the residue of said molecule; T is R-S- or
<IMG> wherein R is a monovalent hydrocarbon radical and
R' represents the carbon atoms necessary to complete an
aromatic or aliphatic ring; X represents a carbon atom;
and n is a whole number from O to 5, said -S- of said R-S-
and <IMG> moieties being positioned alpha, beta, gamma,
delta, epsilon or zeta to said anion;
(3) transferring said complex silver salt to a
superposed image-receiving layer; and
(4) reducing said transferred complex silver salt
to provide a silver image.
48. A photographic process as defined in claim 47
wherein said M represents a 2-amino-4-hydroxy-1,3,5-triazine.
49. A photographic process as defined in claim 47
wherein said M represents a 1,2,3,4-tetrazole.
50. A photographic process as defined in claim 47
wherein said M represents a 5-pyrazolone.
51. A photographic process as defined in claim 47
wherein said M represents a 1,2-disulfonylalkane.
52. A photographic process as defined in claim 47
wherein said M represents a sulfonamido derivative of an amino
acid.
53. A photographic process as defined in claim 47
wherein said M represents a 2,4-dihydroxypyrimidine.
-49-

54. A photographic process as defined in claim 47
wherein said M represents a 4,6-dihydroxypyrimidine.
55. A photographic process as defined in claim 47
wherein said T is R-S-.
56. A photographic process as defined in claim 47
wherein said T is <IMG> .
57. A photographic process as defined in claim 55
wherein R is alkyl.
58. A photographic process as defined in claim 56
wherein R' represents the carbon atoms to complete 2-thienyl.
59. A photographic process as defined in claim 47
wherein said silver halide solvet is
<IMG>.
60. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG> .
61. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>.
-50-

62. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>
63. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>
64. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>
65. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>
66. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>
67. A photographic process as defined in claim 47
wherein said silver halide solvent is
<IMG>
68. A photographic process as defined in claim 47
wherein said aqueous alkaline solution additionally includes
a viscosity-imparting reagent.
-51-

69. A photographic product which comprises a first sheet-like
element comprising a photosensitive silver halide emulsion layer on a
support, a second sheet-like element adapted to be superposed with said
first sheet-like element and means for retaining an aqueous alkaline pro-
cessing solution so positioned as to distribute said processing solution
between said first and second sheet-like elements, at least one of said
elements and said processing solution containing a silver halide solvent
which forms a silver complex soluble in said aqueous alkaline solution,
said silver halide solvent being a difunctional compound wherein one of
said functions is a hard or soft atom that ionizes to the corresponding
anion in said alkaline solution to combine with silver cation and the
other of said functions is a non-ionizable soft base that additionally
combines with said silver cation, wherein said difunctional compound
possesses (a) an 0, N or C atom that ionizes to the corresponding O?, N?
or C? anion in said alkaline solution and (b) an -S- containing moiety
excluding -SH and moieties that form -SH in alkaline solution, said -S-
of said moiety positioned alpha, beta, gamma, delta, epsilon or zeta to
said anion.
- 52 -

70. A photographic product which comprises
a first sheet-like element comprising a photosensitive
silver halide emulsion layer on a support, a second
sheet-like element adapted to be superposed with said
first sheet-like element and means for retaining an
aqueous alkaline processing solution between said
first and second sheet-like elements, at least one of
said elements and said processing solution containing a
silver halide solvent which forms a silver complex
soluble in said aqueous alkaline solution, said silver
halide solvent being a compound of the formula M-(X)n-T
wherein M represents an aliphatic or aromatic moleucle,
Y-A, wherein A is an atom selected from 0, N and C
ionizable in said alkaline solution to the corresponding
O?, N? and C? anion and Y represents the residue of
said molecule; T is R-S- or
<IMG> wherein R is a
monovalent hydrocarbon radical and R' represents the
carbon atoms necessary to complete an aromatic or ali-
phatic ring; X represents a carbon atom; and n is a
whole number from 0 to 5, said -S- of said R-S- and
<IMG> moieties being positioned alpha, beta, gamma
delta, epsilon or zeta to said anion.
71. A photographic product as defined in
claim 70 wherein said M represents a 2-amino-4-hydroxy-
1,3,5-triazine.
-53-

72. A photographic product as defined in
claim 70 wherein said M represents a 1,2,3,4-tetrazole.
73. A photographic product as defined in
claim 70 wherein said M represents a 5-pyrazolone.
74. A photographic product as defined in
claim 70 wherein said M represents a 1,2-disulfonyl-
alkane.
75. A photographic product as defined in
claim 70 wherein said M represents a sulfonamido
derivative of an amino acid.
76. A photographic product as defined in claim 70
wherein said M represents a 2,4-dihydroxypyrimidine.
77. A photographic product as defined in claim 70
wherein said M represents a 4,6-dihydroxypyrimidine.
78. A photographic product as defined in claim 70
wherein said T is R-S-.
79. A photographic product as defined in claim 70
wherein said T is <IMG> .
80. A photographic product as defined in claim 78
wherein R is alkyl.
81. A photographic product as defined in claim 79
wherein R' represents the carbon atoms to complete 2-thienyl.
82. A photographic product as defined in claim 70
wherein said silver halide solvent is
<IMG>
-54-

83. A photographic product as defined in claim 70
wherein said silver halide solvent is
<IMG> .
84. A photographic product as defined in claim 70
wherein said silver halide solvent is
<IMG> .
85. A photographic product as defined in claim 70
wherein said silver halide solvent is
<IMG> .
86. A photographic product as defined in claim 70
wherein said silver halide solvent is
<IMG> .
87. A photographic product as defined in claim 70
wherein said silver halide solvent is
<IMG> .
-55-

88. A photographic product as defined in claim
70 wherein said silver halide solvent is
<IMG> .
89. A photographic product as defined in claim
70 wherein said silver halide solvent is
<IMG> .
90, A photographic product as defined in claim
70 wherein said silver halide solvent is
<IMG> .
91. A photographic product as defined in claim
70 wherein one of said first and second sheet-like elements
additionally includes an image-receiving layer.
92. A photographic product as defined in claim
91 wherein said image-receiving layer is included in said
second sheet-like element.
93, A photographic product as defined in claim 92
wherein said image-receiving layer is a silver precipitating
layer.
-56-

94. A photographic product as defined in claim 92
wherein said image-receiving layer is a dye image-receiving
layer and said first sheet-like element additionally
includes a dye image-forming material associated with said
silver halide emulsion layer.
95. A photographic product as defined in claim 70
wherein said aqueous alkaline processing solution includes
a viscosity-imparting reagent.
-57-

Description

BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to photography, and in particular,
it is concerned with a new class of silver halide solvents and wîth photo-
graphic products, processes and compositions employing the same.
Description of the Prior Art
Photographic processing compositions capable of forming water-
soluble complex silver salts are known to be useful in many types of
silver halide photography. To obtain a relatively stable image in an exposed
and developed photosensitive silver halide emulsion, the silver halide
remaining in the unexposed and undeveloped areas of the emulsion should
be converted to a soluble silver complex that can be removed by washing
or converted to a stable silver complex that will not "print-out" upon
prolonged exposure to light. In conventional or "tray" development, i~
is customary to fix the developed silver halide emulsion by applying a
solution of silver halide solvent, i.e., silver halide complexing agent
which forms a water-soluble silver complex with the residual silver
halide. The water-soluble silver complex thus formed and excess silver
halide solvent are then removed from the developed and fixed emulsion by
washing with water.
Silver halide solvents also have been employed in monobaths
where a single processing composition containing a silver halide developing
agent in addition to the silver halide solvent is utilized for both develop-
ing and fixing an exposed photosensitive silver halide layer. Silver halide

~7~
solvents also have been employed in diffusion transfer photo-
graphic processes. Such processes are now well known in the
art; see for example, U. S. Patents Nos. 2,543Jl81; 2,647,056;
2,983,606, etc. In processes of this type, an exposed silver
halide emulsion is treated with a processing composition whereby
the exposed silver halide emulsion is developed and an image-
wise distribution of diffusible image-forming components is
formed in the unexposed and undeveloped portions of the silver
halide emulsion. This distribution of image-forming components
is transferred by imbibition to an image-receiving stratum in
superposed relationship with the silver halide emulsion to
provide the desired transfer image. In diffusion transfer
processes where a silver transfer image is formed, processing
is effected in the presence of a silver halide solvent which
forms a diffusible complex with the undeveloped silver halide.
The soluble silver complex thus formed diffuses to the super-
posed image-receiving layer where the transferred silver ions
are deposited as metallic silver to provide the silver transfer
image. In preparing silver prints in this manner, the image-
receiving element preferably includes a silver precipitatingagent, for example, heavy metal sulfides and selenides as
described in U. S. Patent No. 2,698,237 of Edwin H. Land.
various compounds have been employed as silver
halide solvents in the photographic processes described above.
One of the most commonly employed is sodium thiosulfate.
Other silver halide solvents that have been used include
thiocyanates, such as potassium and sodium thiocyanate;
andcyclic imides~ such as barbituric acid and uracil.
--2--

z
The present invention is concerned with a new class of silveT halide
solvents useful in both conventional and diffusion transfer pho~ography.
Summary of the ~nvention
It is, therefore, the primary object of the present invention to
provide photpgrahpic products, processes and compositions employing a new
class of silver halide solvents.
Other objects of this invention will in part be obvious and will in
part appear hereinafter.
The invention accordingly comprises the processes involving the
several steps and the relation and order of one or ~ore of such steps with
respect to each of the others3 and the products and compositions possessing
the features, properties and the relation of elements which are exemplified
in the following detailed disclosure, and the scope of the application of
which will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention,
reference should be had to the following detailed description.
Detailed Description of the Invention
By the present invention, i~ has been found that difunctional
compounds wherein one of said functions is a hard or soft atom that ionizes
to the corresponding anion in alkaline solution for combining with silver
cation and the other of said functions is a non-ionizable soft base for
additionally combining with said silver cation form silver complexes soluble
in alkaline solution and are use~ul for complexing undeveloped silver halide
in photographic pTocesses. These compounds may be aliphatic, cyclic and
acyclic, or they may be aromatic.
According to the present invention, there is provided a photographic
processing composition comprising an aqueous alkaline processing solution
including therein a silver halide solvent which forms a silver complex soluble
in said aqueous alkaline solu~ion, said silver halide solvent being a di-
f~mctional compound wherein one of said functions is a hard or soft atom thationizes to the corresponding anion in said alkaline solution to combine wi~h
silver cation and the o~her of said functions is a non-ionizable soft base
~ 3 _
r~~
'~..,~

additionally combines with said silver cation> wherein difunctional compound
possesses (a) an 0, N or C atom that ionizes to the corresponding 0 ~ , N ~3
or C ~3 anion in said alkaline solution and tb) an -S- containing moiety
excluding -SH and moieties that form -SH in alkaline solution, said -S- of
said moiety positioned alpha, beta, gamma, delta, epsilon or zeta to said
anion.
The invention also provides a photographic process for forming a
water-soluble complex silver salt with the unexposed and undeveloped silver
halide of a photosensitive element which comprises contacting said silver
halide with the abovedefined aqueous alkaline processing solution.
In another aspect, the invention provides a photographic product
which comprises a first sheet-like element comprising a photosensitive silver
halide emulsion layer on a support, a second sheet-like element adapted to be
superposed with said first sheet-like element and means for retaining an
aqueous alkaline processing solution so positioned as to distribute said
processing solution between said first and second sheet-like elements, at
least one of said elements and said processing solution containing a silver
halide solvent which forms a silver complex soluble in said aqueous alkaline
solu~ion, said silver halide solvent being a di~unctional compound wherein
one of said functions is a hard or soft atom tha~ ionizes to the corresponding
aDion in said alkaline solution to combine with silver cation and the other
of said ~unc~ions is a non-ionizable soft base that additionally combines with
said silver cation, wherein said difunctional compound possesses ~a) an 0, N
or C atom that ionizes to the corresponding 0 ~, N ~3 or C ~3 anion in said
alkaline solution and (b) an -S- containing moiety excluding -SH and moieties
that form -SH in alkaline solution, said -S- of said moiety positioned alpha9
beta, gamma, delta, epsilon or ze~a to said anion.
- 3a -
. ~1 ,

The hard-soft [HSAB] principle that "hard acids pre-
fer to bind to hard bases and soft acids prefer to bind to soft
bases" is now well-known, and its application and usefulness in
understanding a variety of chemical phenomena has been widely
5 discussed notably by R. G. Pearson, JO Am. Chem. SocO 85,
3533(1963); Chemistry in Britain 3,103(1967~; and ~. Chem.
Education 45,581(1968). Under "The Principle of ~Iard and
Soft Acids and Bases", a "soft basei' is defined as one in
which the valence electrons of the donor atom are easily
10 distorted or removed as opposed to a "hard base" in which the
valence electrons of the donor atom are tightly held. A
"soft acid" is one in which the acceptor atom generally is
large in size and has several valence electrons which are
easily distorted or removedJ and a "hard acid" is one in ~hich
15 the acceptor atom is small in size and does not contain
unshared pairs of electrons in the valence shell, i.e., does
not contain valence electrons that are easily distorted or
removedO Because of these properties, hard acids and hard
bases exhibit high electronegativity and low polarizability,
20 and conversely, soft acids and soft bases exhibit low
electronegativity and high polarizability. The acids and bases
may be an atom, molecule or ion, with cations, for example,
being acidsD Under the HSAB principle, silver cation (Ag )
is classified as a soft acid, and thus, prefers to coordinate
25 with a soft base, i.e., the complexes of Ag~ with soft donor
atoms will generally be more stable than those with hard
donor atoms. As a general rule, soft acids coordinate best
to one of the heavier atoms of a family of elements so that
the general order of stabilities of complexes A:B wherein A
30 is a soft acid are:
_a,_
. , :

N P ~As >Sb > Bi
O~ S ~ Se~- Te
As noted above, in the subject difunctional
compounds the ionizable atom may be a hard atom as exemplified
by 0 which ionizes to the corresponding 03 anion in basic
solution, or it may be a soft atom as exemplified by C which
ionizes to the corresponding C~ in basic solution. It will
be appreciated that the difunctional compound selected will
possess a hard or soft atom that ionizes at the pH at which
the particular photographic process is performed. The non-
ionizable soft base for additionally combining with the silvercation may be, for example, an -As , -P , -Se-, or -S- con-
taining moiety.
In a preferred embodiment of the present invention,
the difunctional compounds comprise an aliphatic or aromatic
molecule containing as the ionizable atom, an 0, N or C
atom possessing a proton removable in alkali to provide
the corresponding o~, ~ or C~ anion, which molecule is
substituted with, as the non-ionizable soft base, a moiety
containing S-, excluding -SH and moieties that would form
-SH in alkali. The position of -S- with respect to the
anion of the parent molecule should be such that the -S-
is capable of combining with the silver cation together with
the anion. In general, the -S- is adjacent to or up to
6 atoms away from the anionO Where the compound comprises
an aromatic molecule, the position of -S- ordinarily is one

~7~
atom up to 6 atoms away from the anion. Where the compound
comprises an aliphatic molecule, the position of -S~ ordinarily
is adjacent to or 2 atoms up to 6 atoms away from the anion.
Preferred -S- containing moieties are thioether
moieties, particularly T-(X)n- wherein T represents R-S- or
~ Compounds substituted with the preferred thioether
moiety may be represented by the formula M-(X)n-T wherein M
represents an aliphatic or aromatic molecule, Y-A, wherein A
is an atom selected from O, N and C ionizable in alkaline solu-
tion to the corresponding anion 0~, ~ and C~ and Y represents
the residue of said molecule; T represents R~S- or
,R~
t- wherein R is a monovalent hydrocarbon radicalJ
` S -
cyclic including aliphatic or aromatic, and acyclic including
carbon atoms ~orming a continuous or a branched chain and R'
represents the carbon atoms necessary to complete an aromatic
or aliphatic ring; ~ represents a carbon atom; and n is a whole
number preferably from 0 to 5 so that the -S- of said thioether
moiety is in a position alpha, beta3 gamma, delta, epsilon or
zeta to said anion. Preferably, R is a monovalent aliphatic
radical including cyclic and acyclic aliphatic radicals, eOg.,
alkyl and cycloalkyl, such as, methyl, ethyl, isopropyl,
t-butyl, cyclopentyl and cyclohexylJ and R' represents the
carbon atoms to complete a 5- or 6- membered ring, e.gO,
aromatic, such as,2-thienyl ( ~ ) or aliphatic, such as,
~-thianyl ( ~ ) .
S
--6--

E~amples of aromatic molecules possessing the said
ionizable atom which may be substituted with said thioether
moiety include 2,4-dihydroxypyrimidine (uracil), ~,6-dihydroxy-
pyrimidine (pseudouracil)~ hydroxy-substituted l,3,5-triazines,
hydroxy-substituted 1,2,4-triazines, 1,2,3,4-tetrazole,
3,6-dihydroxypyridazine, 5-pyrazolone and 4-hydroxy-
quinazolineO Examples of aliphatic molecules possessing the
said ionizable at~m which m~.y be substituted with said thioether
moiety include sulfonamido derivatives of amino acids,
1,3-disulfonylalkanes~ 1,3-disulfonylcycloalkanes and alkanes
containing a sulfonyl group and a cyano, a sulfinyl or a
t-sulfonamido group separated from the sulfonyl group by a
single carbon substituted with at least one hydrogen atom.
The appropriate positioning of the T-(X)n~ moiety,
as exemplified by R-S-(X)n-, with respect to the anion of the
molecule M is illustrated below wherein Ae represents the
anion 0~, ~ or Ca and Y represents the residue of the
molecule:
Y-A0-S-R alpha
Y_Ae-X-S-R beta
Y-A -X-X-S-R gamma
Y-Ae-X-X-X-S-R ~ delta
- Y-A -X-X-X-X-S-R - epsilon
Y-Ae-X-X-X-X-X-S-R zeta
For both aliphatic and aromatic molecules, the -S-
preferably is gamma to the anion~ for exampleg ~CI ~CH2-CH2-S-Ro _
In a particularly preferred embodiment, the
R-S-(X)n- group is alkylthio- or alkylthioalkylene-, and the R'

R' 3
of said l~ ~~(X)n~ group represents the carbons to complete
2-thienyl. It will he appreciated that these groups may be
substituted with, for example, solubilizing groupsJ such as
carboxy, hydroxy or amino.
Par~icularly useful silver halide complexing agents
within the broad class of compounds described above are
2,4-dihydroxypyrimidinesturacils) and 4,6-dihydroxypyrimidines
(pseudo uracils3 substituted on at least one carbon atom with
an -S-containing moiety, preferably the above-denoted -
thioether moiety, T-(X)n- and particularly where R is alkyl
and Rl is 2-thlenyl. Preferred compounds of this type are
2,4-dihydroxypyrimidines substituted in the 5- or 6-position
with said thioether moiety and 4,6-dihydroxypyrimidines
substituted in the 2- or 5-position with said thioether
moiety as shown in the following formulas:
~H IOH
T (X)~ ~ ~ T-(X~n ~ OH
(I) (II)
OH OH
H ~ T-(X)
(III) (IV)
It will be appreciated that the uracils and pseudo uracils in
addition to the thioether substituent, may be substituted on
:20 the remaining carbon atom with groups, such as, halo, hydroxy,
--8--
:: :,:. . .. .
, ~ . . . : : " . ` . ::

~C)7~ ;Z
.
amino, alkyl and alkyl su~stituted with, e.g., solubilizing
groups, such as, hydroxy, carboxy5 amino and aliphatic ethers.
Also, it will be appreciated that although the foregoing
~ormulas are in enolic form, it is intended to encompass
the keto modifications of these compounds as well.
Specific examples of compounds use~ul as silver
halide solvents in accordance with the present invention
include:

ii2
o~
( 1 ) CH3SCH2 ~ N ~LOH
OH
:: (2 j Cl~N ~ r
CH3SCH2J~ N ~J_OH
` ~
OH ::
( 3 ) ~ ~N
CH3S (CH2) 2 ~ N ;~LOH
,~ .
~4) CH3SCH2~N
N ~L OH
--10--

OH
(5) ~N
CH3S~N ~LOH
OH
(6) Cl~N
HOOCCH2 SCH2~ N ~L
OH
(7) ~N
HOOCCH2S (CH2) 2 ~ N ~LOH
OH
~CH25CH2 ~"L OH

:
~a~7~4~ii2
OH
CH3S~N
' ~N~J--OH
' ', ~ .
: . :
(10) OH
s~
:,:
~;
OH ~.
(llj Br~N
.
:
' :
f)H
(12 ) CH3S ~
~H2J"~LOH
--12--

SLI:)7~L452
;
OH
(13) ¢~N
NE~2 (C~I ) SCH - ~; OH
OH
(14)n-C3H7SCH2~N ~L
OH
(15)
HOCH2CI HCH2SC~2J~ N ;~LOH
OH
~1
(16) rl N
n-C4 H g SCH2J~ N~L OH

sz
OH `''
(17) CH3S (CH2) 2SCH2
OH
(18) Cl--~N
CH3S (CH2) 2SCH2 ~ N ~L
OH
(19) ~ U ~3
~H
(20) HO~l N~LCH2---ls
0~1
(21) ~N
CE3SCH21l N ~ ~ 2
--14--

~:;
OH
~ .
(22 ) ~ N
OH
(23) ~N
HO N J--(CH2) 2SCH3
,.~ '
OH
(24)CH3S (CH2) ~l~M :
-
.` :
(25)
~L ~
HO ,J CH2SCH3
--15--

5;~
OH
( 2 6 ) HO (CH2 ) ~
H~ N ~LCH2SCH3
(27) OH
OHO~N ~LCH2SCH3 ~'
(CH3) 2
(28)
OH OH OH
CH2 CHCH~N
N ~L 2 SCH3
(29) OH
- CH3S (CH2) 4~N
HO ~ N ~L CH2SCH3
(30) ~ :
CH 3 S CH~
H N ~:J
-16-

`
( 31 )
: OH
CH30 (CH2) 2 (CH2) ~N
H NJ--CH2SCH3
(32 )
HoJ~5L~2 IIH~LOH
(33)
OH O, H
NO~CH2_S_CH2~LOH
(34)
OH OH
HO ~LCH2 -S--CH2 ¢N~/J 0~1
--17--

~7~S~
(35)
o 1" C}12-5- (CH2) 2-S-CH2~ OH
(36)
OHOH ..
HO ~ I CH2--5- (CH2 ) 3 5 C 2~N 'L
(37)
OHqH
H~ CH2--S--(CH2)2 5 CH2~0H
.~ .
(38)
OH I H
~ /~
HO ~ ~C~I2-S--CH2-CE~CH2-CH2--S-CH2- \ N "L--OH
--18~

(39) OH
CH3S~\ N
N~ N ~LOH
(40)
OH
CH3SCH2 ~\N
N~ N ~L OH
(41) OH
N
~,,J~ ~L (CH ) SCH3
(42 )
OH
~\~ N
J~ N~L CH2SCH3
.
19-- .

:::
C~12 SCH3
N N
N ~L
(44) "~
N M
H2NJ~ ~CH2SCH3
(45) N=~
\ CH2SCH3 :~
(46? Nl I :
N~
CH2SCH2COOEI ~I
OH
(47) C~13
~ ' ' .
OH
- (48)
C~I3SCH2 N OH
--20--

L52
(4 9) Qt~CH2SCH3
HN N H
(50) Q CH3
C 2 3
HN~NH
(51)~ ( 2) 2 3
XN ~7H
(52)2¢s~,
CH3SCH N
- H

i2
(53)
3S ~1~CH2SCH3
N
H
// \\
(55~ ~ !
HOJ~ N
\N/
~3 .
(56)
3 ~ C02CH2CH3
N~'

s~ :
(57)
~) 2SCH~COOH
2~; S2
(5~3)
H ~3
20S SO2
21 J 2
~2
(59) ~2) 2SCH3
201S SO2
2 2
(60) H~) 3SCH3
20S SO2

S~2 "
(61)
H\~H2 ) 3SCH2CH3
~~
H2~ 2
H2 H2
(62~
E~3
o2/s S02 ~
H2 ~H2
(63) H ~H2) 3SCH2COOH
o2s S02
2~ JH2
H2 H2
(64 )
H ~H2 ) 2SCH3
H2 H2
~4
- ~ . . . .

.
: L~7~5Z
(6 ) CH3S02fHS02CH3
CH2CH2SCH3 ,
(66) f
CH2CH2SCH3
CH3S02
CH2CH2CH2SCH3
(68) CH3S02CHC~ . ~
CH2CH2SCH3 .1
,
(69) CH3S02CHS02N N-cH3~Hcl .
(CH2) 2S (CH2) 2COOH :
. ~:
(70)
CH3SO2lHs02N~ cH2cooH o~Cl
2 2 3
(71) CH3SCH2fHCH
MH2
-25-
-, .... , ~ ,
. . ~

L52
.,
(72) CH3S(cH2)2clHN~Is02 ~ 3
COOH
(73) CH3scH2cHM~Iso2 ~ 3
OOH
(74) CH3 ~ 02~H(CH2)2SCH2COOH ; :
(75) CH3SCH2CIH~HS02 ~ COOH
COOH
(76) CH3SCH2CHNHS02 ~ 3
COOH
(77) CH3SCH2CIE~HS2
COOH
(78) CH3So2NH(cH2)2sc 2
-~6-

7:~L4L5~2
The thioether-substituted 2,4-dihydroxypyrimidines
(uracils) may be preparedJ for example, by reacting a 5-
or 6-mercaptoalkyl-substituted 2,4-dihydroxypyrimldine with
a halideJ e.g~, RI or RCl, to give the corresponding RS-alkyl-
substituted compound or by reacting a 5- or 6-haloalkyl-
substi-tuted 2,4-dihydroxypyrimidine with a mercaptan, RSEI,
to give the corresponding RS-alkyl-substituted compound,
using the procedure reported by Giner-Sorolla et al., J.
Med. Chem. 9, 97 (1966). These compounds also may be pre-
pared by reaction of the appropriate ~-keto esters, e.g.,
CH-fH-C02Et and CH3SCH2CCH2COEt with thiourea, NH2CNH2,
O SR O S
followed by alkylation and acid hydrolysis. These procedures
are similar to those reported by M. Jackman et al., J. Amer.
Chem. Soc. 70, p. 497 (1948) and R. M. Dodson et al., ibid.,
72, p. 3.?81 (1950). The thioether-substituted 4,6-dihydroxy-
pyrimidines (pseudo uracils) may be prepared, for example,
~H
by reactin~ an RS-substituted amidine, RS-CH~C~ , with a
diethyl malonate, R'CH(CO_Et)2 using the procedures described
in J. Chem. Soc. 1943, p. 388; J. Org. Chem. 18, p. ~53; and
J. Org. Chem. 17, p. 1320. The pseudo uracils also may be
prepared using the procedure of &ershon et al., JO Org. Chem.
26, 1874 to prepare the 5-bromomethyl-4,6-dichloropyrimidine
and then displacing the bromo group with a mercaptide, RS~M~,
followed by acid hydrolysis to the dihydroxy product.
Uracil and pseudo uracil sulfides may be prepared,
for example, by reacting chloro- and mercapto-substituted
uracils, such as, 5- (or 6-) chloromethyluracil and 5- (or 6-)

mercaptomethyluracil as described in the aforementioned
Giner-Sorolla reference. The bis uracils, such as, those
of formulas 35 to 38, may be synthesized by reacting
chloromethyl-substituted uracils with a dithiol, such as,
1l2-ethanedithiol or 1,3-propanedithiol. Mercapto-substi-
tuted hydroxy and/or amino pyrimidines also can be alkylated
with an alkyl halide in aleoholic solution of sodium alkoxide
or with chloroalkanoic acids using the procedures described
in The Chemistry of Heterocyclic Compounds, Vol. 16, p. 282-83
A. Weissberger, Wiley-Interscience 1962. Various other pro-
cedures for preparing thioether-substituted uracils and pseudo
uracils and their sulfides and other -S-eontaining derivatives
are described in the latter reference and in Supplement 1 of
Vol. 16 (1970). Uraeils with cyclic thioether moieties bonded
to adjacent carbon atoms may be prepared from the correspond-
ing hydroxy/mercapto-substituted compounds by treating with
chloroaeetie acid as described in the J. Amer. Chem. Soc.
82, p. 158 (1960).
The thioether-substituted symmetrical triazines
may be prepared, for example~ from the haloalkyl-substituted
dihydroxy or amino/hydroxy triazine by reaetion with the
sodium derivative of a mereaptan, RS9Na~, using the procedure
reported by M. A. Stevens et al., J. Heteroeyclic Chem. 4,
268 (1967). Chloroalkyl-substituted dihydroxy sym. triazines
useful for reaction with the mercaptide may be prepared using
the procedure reported in the J. Amer. Chem. SocO, 79, p. 944.
The thioether-substituted asymmetrieal triazine compounds may
be prepared from 6-mercapto-3,5-dihydroxy (or hydroxy/amino3-
1,2J4-triazines using the procedure described by C. Cristescu
et al., Pharmazie 17(4), p. 209 (1962).
-28-

s~
Thioether-substituted tetraæoles may be prepared by
reacting a nitrile, e.g., RSCH2CN with Na~3, by alkylation of
a 5-mercapto tetrazole; or by reacting a 5-haloalkyltetrazole
with a mercaptan, RSH. The thioether-substituted 5-pyrazolones
may be prepared by reacting an (R-thio) acetoacetic acid
ester and hydrazine or substituted hydrazines using the pro-
cedure reported by Gundermann et al., BerO 95, 2076 (1962).
The thioether-substituted 3,6-dihydroxypyridazines may be
prepared by reacting a halo-substituted compound with a
mercaptide, RS~ ~, to displace the halo substituent. Thioether-
substituted hydantoins are disclosed in the Can. J. Research
27 (B), p. 421 and may be prepared according to the method
disclosed therein.
The thioether-substituted 4-hydroxyquinazolines
may be prepared by heating an ester of anthranilic acid with
an RS-substituted amidine in an ethanolic solution of a
sodium alkoxide. The thioether-substituted 2-hydroxypyridines
may be prepared by reacting a 2-chloro-6-bromoalkylpyridine
with a mercaptide, RS ~ a~, to displace the bromo substituent
followed by reacting with sodium benzylate and acid hydrolysis
to yield the 2-hydroxy product. The thioether-substituted
dehydrothiomorpholine-2-ones may be prepared by treating a
mercaptoacetic acid ester with ammonia to form the correspond-
ing amide which is ring-closed by reaction with chloroacetone/
triethylamine to yield the 6-methyl-substituted ring system
followed by bromination of the methyl group and reaction with
a mercaptide to give the product. The 4-hydroxyquinolines
may be prepared, for example, by reacting an RS-substituted
-29-

aniline with diethylethoxymethylene malonate followed by
heating in an inert solvent to give the ring-closed
3-C02R intermediate which is treated with alkali, and if
desixed, decarboxylated. The compounds substituted with
, R~
( r~~~ may be prepared, for example, by reacting a
~S -/
2-chloroalkylthiophene with the selected mercapto-substituted
compound and by displacement reactions using 2-bromothiophene.
It will be appreciated that the above represent only some of
the methods a~ailable for preparing thioether-substituted
heterocyclic compounds and that other methods may be selected
from those disclosed, for example, in The Chemistry of
Heterocyclic Compounds, A. Weissberger, Wiley-Interscience.
In preparing thioether-substituted amino acids,
mercapto-substituted amino acids may be treated with an
alkylating agent to give the corresponding alkylthioether
compound. The sulfonamido derivatives of the -S-containing
amino acids may be prepared by reacting the acids with, e.g.,
p-toluene-sulfonyl chloride according to the procedure
reported by E. W. McChesney et al., J. Amer. Chem. Soc., 59J
pO 1116 (1937).
The alkanes containing a sulfonyl and a sulfinyl
group may be synthesized from dithioalkanes wherein the thio
groups are ~ to each other by treating with an oxidizing
agent, e.gO, potassium permanganate to yield the corresponding
sulfide-sulfone and then treating the sulfide-sulfone with
an oxidizing agent, such as, sodium metaperiodate to yield
the sulfonyl-sulfinyl alkane. The 1,3-disulfonyl alkanes
and cycloalkanes may be synthesized from the corresponding
1,3-dithio compounds by treating with an oxidizing agent,
such as, peracetic acid, as described in Ber. 74, p. 1672
-30-

(1941), Ber. 32, p. 1375 (1899) and Tetrahedron Letters, 1962, p. 515.
The alkanes containing a sulfonyl and a cyano group may be prepared ac-
cording to the procedure of R. Dijkstra et al., Chem. Abs. 49:1153 gh
(1955) by reacting a sodium alkylmercaptide with a chloro-substituted
acetonitrile to yield the corresponding thio-nitrile which is then treated
with an oxidizing agent, such as, hydrogen peroxide to give the product
sulfonyl-cyano alkane. The alkanes containing a sulfonyl and an N-
piperazinyl sulfonamido group may be prepared by reacting a sulfene with
a piperazine using the procedure reported by G. C.pitz et al., Angew, Chem.
Internat. Edit. Vol. 5 (1966), p. 594. The thioether-substituted alkanes
may be prepared by reacting ~he compounds con~aining a sulfonyl and a
sulfinyl, cyano, sulfonamido or second sulfonyl group with the chloro-
substituted derivative of the selected thioether substituent, e.g.,
R-S-(CH2)2-Cl-
Sulfonyl-piperazinylsulfonamido compounds, such as, those of
formulae 69 and 70 form the subject matter of United States Pa~ent Serial
No. 3,976,647 of Richard B. Greenwald. Sulfonyl-cyano compounds, such as,
those of formulae 67 and 68 form the subject matter of United States Patent
Serial No. 3,975,423 of Alan L. Borror and Richard B. Greenwald. 1,3-
Disulfonyl-cycloalkanes, such as, those of formulae 57 to 64 form the
subject matter of United States Patent Serial No. 3,958S,992 of Richard B.
Greenwald filed December 23, 1974.
It will be understood by those skilled in the art that the
selection of a given silver halide solvent of ~he present invention will
be based on the requirements of the particular
- 31 -

photographic process and may be determined empirically. For
example, for use in silver diffusion transfer processes, one
will select a silver halide solvent which has a silver
complexing and diffusion rate appropriate for obtaining a
desired transfer image density within the desired specified
time.
In formulating photographic processing compositions
utilizing the above-described compounds, the compounds may be
used singly or in admixture with each other or in admixture
with other silver halide solvents. The total amount employed
may vary widely depending upon the particular photographic
system and should be used, for example, in a quantity
sufficient for fixing a developed negative in conventional
; "tray" processing or in a quantity sufficient to give a
! 15 satisfactory transfer print in diffusion transfer processes
nder the particular processing conditions employed.
Though the silver halide solvents of the present
invention are broadly useful in a variety of photographic
processes of the type in which water-soluble silver complexes
are formed from the unreduced silver halide of a photoexposed
and at least partially developed silver halide stratum, they
find particular utility in diffusion transfer processes. A
composition embodying the present invention specifically suit-
able for use in the production of transfer images comprises,
in addition to the silver halide complexing agents of the
above-described type, a suitable silver halide developing
agent, preferably an organic developing agent~ Examples of
developing agents that may be employed include hydroquinone
and substituted hydroquinones, such as, tertiary butyl
hydroquinone, 2,5-dimethyl hydroquinone~ methoxyhydroquinone,
-32-
. ~

:` :
ethoxyhydroquinoneJ chlorohydroquinone; pyrogallol and
catechols, such asJ catecholJ 4-phenyl catechol and tertiary
butyl catechol; aminophenolsJ such asJ 2,4J6-triamino-ortho-
cresol; lJ4-diaminoben2enesJ such asJ p-phenylenediamine,
lJ2,~-triaminobenzene and 4-amino-2-methyl-N,N-diethylaniline;
ascorbic acid and its derivatives, such as, ascorbic acid,
isoascorbic acid and 5J6-isopropylidene ascorbic acid~and
other enediols, such asJ tetramethylreductic acid, and
hydroxylamines, such asJ NJN-dit2-ethoxyethyl)hydroxylamine
and N,N-di-(2-methoxyethoxyethyl)hydroxylamine.
In diffusion transfer processes, the processing
composition if it is to be applied to the emulsion by being
spread thereon in a thin layer also usually includes a
viscosity-imparting reagent. The processing composition may
comprise, for exampleJ one or more silver halide solvents of
the present invention, one or more conventional developing -
agents such as those enumerated above, an alkali such as
sodium hydroxideJ cesium hydroxideJ or potassium hydroxide
and a viscosity-imparting reagent such as a high molecular
weight polymer, e.g.J sodium carboxymethyl cellulose or
hydroxyethyl cellulose.
In one such transfer process, the processing solu-
tion is appliad in a uniformly thin layer between the super-
posed surfaces of a photoexposed photosensitive element and an
image-receiving element, for example, by advancing the elements
between a pair of pressure-applying rollers. The elements are
maintained in superposed relation for a predetermined period,
preferably for a duration of about 15 to 120 secondsJ during
which exposed silver halide is reduced to silver and unreduced

silver halide forms a water-soluble, complex salt which
diffuses through the layer of solution to the image-receivlng
element there to be precipitated as an argental image. At
the end of this periodJ the silver halide element is separated
from the image-receiving element. Materials useful in such a
transfer process are described in U. SO Pat. No. 2,543,181,
issued in the name of Edwin H. Land on Feb. 27, 1951, and in
numerous other patents.
The photosensitive element may be any of those con-
ventionally used in silver diffusion transfer processes andgenerally comprises a silver halide emulsion carried on a
base, e.g., glass, paper or plastic film. The silver halide
may be a silver chloride, iodide, bromide, iodobromide,
chlorobromide, etc. The binder for the halide, though
usually gelatin~ may be a suitable polymer such as polyvinyl
alcohol, ~olyvinyl pyrrolidone and their copolymers, etc.
The image-receiving element preferably includes cer-
tain materials, the presence o~ which, during the transfer
process has a desirable effect on the amount and character of
silver precipitated on the image-receiving element. Materials
of this type are specifically described in U. S. Pat. Nos.
2,690,237 and 2,698,245, both issued in the name of Edwin H.
Land on December 2~, 1954 and U. S. Patent No. 33671,241 of
Edwin H. Land issued June 20, 1972.
Separating of the silver halide element from the
image-receiving element may be controlled so that the layer
o~ processing composition is removed from the image-receiving
element or the layer of processing composition is caused to
remain in contact with the image-receiving element, e.g., to
provide it with a protective coating. Techniques which enable
~3~

such results to be accomplished as desired are described in United States
Patent No. 2,647,056 issued to Edwin H. Land on July 28~ 1953. In general,
the processing reagents are selected so that traces remaining ater the
solidiEied processing layer has been separated from the silver image or
which remain in said layer adhered as a protective coating on the silver
image, as indicated above, are colorless or pale, so as not to appreciably
affect the appearance of the image and to have little or no tendency to
adversely react with the silver image.
The silver halide solvents of the present invention also may be
lO. employed in diffusion transfer processes adapted to provide positive silver
transfer images which may be viewed as positive transparencies without
being separated from the developed negative silver image including such
processes adapted for use in forming additive color projection positive
images. Diffusion transfer processes of this type are described in United
States Patents Nos. 3,536,488 of Edwin H. Land and 3,615,428 of Lucretia J.
Weed and in United States Patent No. 3,894,871 of Edwin H. Land filed
July 27, 1973 and in United States Patent No. 3,990,895 of Edwin H. Land
filed April 23, 1974. The subject compounds also find utility as silver
halide solvents in diffusion transfer processes utilizing the properties
20. of the imagewise distribution of silver ions in the soluble silver complex
made available in the undeveloped and partially developed areas of a
silver halide emulsion to liberate a reagent, e.g.l a dye in an imagewise
fashion, as described in United States Patent No. 3,719,489 of Ronald F. W.
Cieciuch, Roberta R. Luhowy, Frank A. Meneghini and Howard G. Rogers.
The following example is given to illus~rate ~he utility of
the compounds of the present invention as photographic silver halide solvents
and is not intended to be limiting.

~7~
Example
A photosensitlve silver halide emulsion on a
support was exposed to a step wedge and processe~ by
spreading a layer oE processing composition approximately
0.0012 inch thlck between the exposed emulsion and a super-
posed image-receiving element comprising a layer of regene-
rated cellulose containing colloidal palladium sulfide carried
on a transparent support. The processing composition was
prepared by adding a silver solvent of the present invention
in a concentration o~ 5% by weight to the following formu-
lation.
Water 814.0 g.
Potassium hydroside
(Aqueous 50% w/w solution) 348.0 g.
Hydroxyethyl cellulose 35.0 g.
Zinc acetate 15.0 g.
Triethanolamine 5.6 g.
Bis-~,N-methoxyethyl
hydroxylamine50.0 g.
After an imbibition period of approximately 1
minute, the developed silver halide emulsion was separated
from the image-receiving element, and the maximum and minimum
transmission densities were measured for the positive image.
The compounds added to the base formulation as silver
halide solvents, and the density measurements obtained with
each of the compounds are set forth in the following table.
- TABLE I
Compound Density
(Formula No.) Maximum Minimum
(1) 2.04 0.57
(~) 1.41 0.26
(3) 1.90 0.27
(4) 2.20 0061
-36-

45;~:
TABLE I (continued)
Compound Density
(Formula No.) Maximum Minimum
(5) 2.10 0.08
(6) 0.78 0.04
t7) 1.20 0.01
(9) 2.21 0.33
(10) 1.24 0.12
(11) 1.20 0.17
(12) 0.94 0.02
(13) 1.85 0.68
(14) 1.70 0.44
(15) 2.69 0.51
(20) 2.25 0.23 r
(22) 1.24 0.12
(23) 1.24 0.13
(24) 2.22 0.16
(25) 2.40 0.24
(26) 2.19 0.35 ;~
(27) 1.66 0.05
(28) 2.09 0.15
(29) 2.95 0.79
(31) 2.05 0.12
(36) 1.00 0.01 :
In a visual comparison between the positive
images obtained with the compounds listed in the foregoing
table and a positive image obtained with uracil, it was
observed that the uracils and pseudo uracils o~ the present
invention gave positive images having more neutral tone than
the positive image produced with uracil.

The photographic procedure described above was
repeated employing other classes of silver halide solvents
of the present invention. The compounds added to the base
formulation, and the maximum and minimum transmission densi-
ties measured for each of the compounds are set forth in
TABI,E II below.
TABLE II
Compound Density
(Formula No.) Maximum Minimum
(21) 1.51 0.96
(43) 1.72 0.37
(45) 0.80 0.41
(49) 0.86 0.10
(54) 0.90 0.58
(57) 1.20 0.10
(65) 2.53 1.80
(68) 2.36 1.76
(76) 1.66 0.22
It will be apparent that the relative proportions
of the subject silver halide solvents and of the other
ingredients of the processing compositions may be varied to
suit the requirements of a given photographic system. Also,
it is within the scope of this invention to modify the formula-
tions set forth above by the substitution of alkalies~ anti-
foggants and so forth other than those specifically mentioned.
Where desirable, it is also contemplated to include in the
processing compositions, other components as commonly used in r
the photographic art.
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Rather than being æissolved in the aqueous alkaline
processing composition prior to application thereof to an
exposed silver halide emulsion, it is also contemplated that
the silver halide solvents of the present invention may be
disposed prior to exposure in a layer or layers of the
photographic film unit, e.g., by placing them behind a silver
halide emulsion layer in the photosensitive element. In
this instance, the processing composition containing the silver
halide solvent is formed by application to the photosensitive
element of an aqueous alkaline soLution capable of solubi-
lizing the silver halide solvent. In diffusion transfer
processes, the subject silver halide solvents usually are
contained in the processing composition.
Since certain changes may be made in the above
compositions and processes without departing from the scope
of the invention herein involved, it is intended that all
matter contained in the above description should be interp-
reted as illustrative and not in a limiting sense.
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