Color-photographic recording material containing non-diffusing electron donor precursor compounds

Compounds corresponding to the formula: ##STR1## wherein Z represents a radical which completes a condensed aromatic ring system; PA1 R.sup.1 represents an n-valent aliphatic or aromatic radical; PA1 R.sup.2 represents H, alkyl or aryl, PA1 R.sup.3 represents one or more radicals to control the diffusion properties and the activation pH; and PA1 n represents 1 or 2, are suitable ED precursor compounds for use in color-photographic recording materials. They are preferably used in a combination with reducible dye-releasers. They are also suitable as so-called scavengers.

This invention relates to a color-photographic recording material 
comprising at least one photosensitive silver halide emulsion layer which 
contains non-diffusing electron donor precursor compounds, from which 
strong reducing agents are formed under alkaline development conditions. 
The invention relates in particular to a recording material, in which the 
electron donor precursor compounds mentioned are used in combination with 
non-diffusing reducible color-providing compounds which, in reduced 
condition, release diffusible dyes under alkaline development conditions, 
which dyes are used as such for the formation of the image or are first of 
all converted into the metal complexes thereof. 
DE-A No. 2,809,716 describes color-providing compounds containing an 
electron-accepting nucleophilic precursor group, which compounds, in 
reduced condition, are subject to an intramolecular nucleophilic 
displacement reaction under alkaline development conditions, with the 
release of a diffusible dye. 
The reduction is caused by so-called electron donor compounds (ED 
compounds) which are contained in the layers in addition to the 
color-providing compounds and are oxidized image-wise during development 
and are thus consumed. 
The remaining image-wise distribution (positive residual image) of the ED 
compounds reacts with the color providing compound and initiates the 
image-wise release of diffusible dyes. The ED compounds which are 
described in that publication are, for example, derivatives of 
benzisoxazolone, hydroquinone, p-aminophenol and ascorbic acid. In order 
to allow the production of qualitatively high-grade images according to 
the process described in the above-mentioned publication, the ED compounds 
must not only be oxidized by exposed silver halide or by silver halide 
developer oxidation products, but they must also themselves be capable of 
reducing the color-providing compounds. Moreover, the respective rates of 
the oxidation or reduction reaction must be optimally coordinated with 
each other so that the ED compound is already oxidized to an appreciable 
extent in the course of development, before it is capable for its part of 
reducing the color-providing compound. The known ED compounds do not 
satisfy these requirements in every respect, which is shown, for example, 
in an inadequate color density and/or in an unacceptable color fog of the 
color transfer images which have been produced. 
The high reducing power of suitable ED compounds simultaneously stipulates 
a high sensitivity to oxidation, which is expressed, during a 
comparatively long storage of the photographic recording material, in a 
premature, non-imagewise consumption of the ED compounds by oxidation and 
in image properties of the transfer image which are impaired thereby and 
which exist in particular in an inadequate color density. It is also 
already known from DE-A No. 2,809,716 that ED compounds may not be used as 
such, but in the form of a less oxidation-sensitive precursor compound 
from which the actual ED compound is formed only under alkaline 
development conditions. Examples of these compounds include the ED 
compounds ED-8, ED-9 and ED-10 of the publication mentioned. However, only 
an inadequate density of the color transfer image is obtained with the 
known ED precursor compounds within an acceptable development time, which 
may be caused either by the actual ED compound not being produced rapidly 
enough from the corresponding precursor compound or by the ED compound 
having too low a reducing power. ED precursor compounds which are 
described in U.S. Pat. No. 4,263,373 are derived from .alpha.-aminoketones 
and their amino-N atom is included as a ring member in a certain 
heterocyclic ring. 
An object of the present invention is to provide new oxidation-stable ED 
precursor compounds which have a good storage stability in the 
photographic material at elevated temperature and/or elevated moisture and 
from which ED compounds having a high reducing power are formed relatively 
quickly only under alkaline development conditions. In particular, these 
compounds are to allow the production of color transfer images of an 
improved color density in the dye diffusion transfer process when used in 
combination with non-diffusing, reducible, color providing compounds. 
This invention provides a color-photographic recording material comprising 
at least one photosensitive silver halide emulsion layer and a 
non-diffusing, color providing compound associated with this layer, which 
recording material contains, in at least one photosensitive silver halide 
emulsion layer or in a non-photosensitive binder layer, a non-diffusing 
electron donor precursor compound (ED precursor compound), from which a 
non-diffusing ED compound is formed under alkaline development conditions, 
characterised in that the ED precursor compound corresponds to the 
following formula I: 
##STR2## 
wherein: 
Z represents a radical which completes a condensed aromatic ring system; 
R.sup.1 represents an n-valent aliphatic or aromatic radical; 
R.sup.2 represents H, alkyl or aryl; 
R.sup.3 represents one or more radicals to control the diffusion properties 
and the activation pH; and 
n represents 1 or 2. 
The ED precursor compounds according to the present invention, which are 
derivatives of isatin, are widely suitable for use in color-photographic 
recording materials where strong reducing agents are to be introduced into 
the layers in masked form, whether as a masked developing agent for silver 
halide or as a masked reducing agent to prevent the undesired diffusion of 
oxidation products which are produced from the silver halide development. 
It is of no importance which type of color-providing compound is used to 
produce the color images. They may be color couplers or color-providing 
compounds which release diffusible dyes as a result of development 
(dye-releasers). However, the preferred use of the ED precursor compounds 
according to the present invention is seen in a combination with 
non-diffusing, reducible color-providing compounds which, in a reduced 
form, release diffusible dyes under alkaline development conditions. 
Thus, the present invention preferably provides a color-photographic 
recording material comprising at least one photosensitive silver halide 
emulsion layer and a combination associated therewith of a non-diffusing, 
reducible color-providing compound which, in its reduced form, is capable 
of releasing a diffusible dye under alkaline development conditions, and a 
non-diffusing electron donor precursor compound (ED precursor compound), 
from which a non-diffusing electron donor compound (ED compound) is formed 
under alkaline development conditions, the ED compound being capable of 
reducing the non-diffusing, color providing compound under alkaline 
development conditions, characterised in that the recording material 
contains a compound corresponding to the general formula I as the ED 
precursor compound. 
The condensed aromatic ring system, which is completed by Z in formula I, 
is preferably a condensed benzene ring. 
The aromatic radical represented in formula I by R.sup.1 may be a 
carbocyclic group, for example (when n=1) a phenyl, naphthyl or an 
anthracenyl group or a 5- or 6-membered heterocyclic group having at least 
one of the hetero atoms N, O, or S as a ring member, for example a furyl, 
thienyl, pyrryl or pyridyl group. When n=2, the corresponding 2-valent 
groups are included. The carbocyclic and heterocyclic aromatic groups may 
be unsubstituted or mono- or poly-substituted, and may contain carbocyclic 
or heterocyclic rings condensed thereon which do not need to be aromatic 
in this case. 
An aryl group represented in formula I by R.sup.2 is in particular a phenyl 
group which may also be mono- or poly-substituted. 
The following are included, for example, as substituents on the radical 
represented by R.sup.1 and R.sup.2, and as R.sup.3 : 
fluorine, chlorine, bromine or iodine, hydroxy, sulfo, sulfamoyl, 
trifluoromethyl, trifluoromethylsulfonyl, amino, nitro. cyano, carboxy, 
carbamoyl, alkoxycarbonyl, alkyl, alkenyl, cycloalkyl, in particular 
cyclohexyl or cyclopentyl, aryl, in particular phenyl, or heterocyclic 
groups, and the last-mentioned groups (alkyl, alkenyl, cycloalkyl, aryl 
and heterocyclic groups) may contain other substituents, for example, 
those of the previously mentioned type, and the alkyl, alkenyl, 
cycloalkyl, aryl or heterocyclic groups mentioned are either joined 
directly or by one of the following divalent connecting links: --O--, 
--S--, --SO.sub.2 --, --SO.sub.2 --NR--, --NR--SO.sub.2 --, --CO--, 
--NR--CO--, --CO--NR--, --NR--COO--, --O--CO--NR--, --NR--CO--NR-- 
(R=hydrogen or alkyl). 
As shown by variations of substituents, the so-called activation pH, i.e., 
the pH at which the CO-N bond of the isatin ring is split up 
hydrolytically and thus the active ED compound is released, may be 
controlled by the choice of the substituents R.sup.3. On the other hand, 
the type of substitution at the aromatic radicals represented by R.sup.1 
and R.sup.2 mainly influences the redox potential of the ED compounds of 
the present invention. 
The alkyl groups optionally represented by R.sup.2 and the alkyl or alkenyl 
groups which are optionally present as a substituent on R.sup.1 and 
R.sup.2 may be straight or branched and may contain from 1 to 22 carbon 
atoms, and may optionally also be further substituted, for example by 
halogen (such as fluorine, chlorine or bromine), hydroxy, amino, alkoxy, 
aroxy, alkylthio, arylthio, a heterocyclic thioether group, alkylsulfonyl, 
arylsulfonyl or a heterocyclic group, such as a 5- or 6-membered 
heterocyclic ring which is joined via a ring nitrogen atom. 
In preferred embodiments of the present invention, R.sup.1 represents an 
optionally substituted phenyl group and R.sup.2 in preferred embodiments 
represents hydrogen. 
According to the present invention, all of the substituents present in the 
ED precursor compound are constituted such that the ED precursor compound 
can be embedded in a non-diffusing manner in photographic layers. For this 
purpose, for example at least one of the substituents present, for example 
at least one of the radicals R.sup.1 and R.sup.3, contains a ballast 
radical. A diffusion-resistant embedding of the ED precursor compound is 
thus particularly desirable, because these compounds are used in an exact 
localisation in a specific layer or in a specific quantity in relation to 
associated, non-diffusing, reducible color-providing compounds which 
should, as far as possible, not undergo any substantial changes even 
during a comparatively long storage of the photographic recording 
material. 
Ballast radicals are considered to be those which allow the compounds 
according to the present invention to be embedded in a diffusion-resistant 
manner in the hydrophilic colloids which are usually used in photographic 
materials. Organic radicals which are preferably suitable for this purpose 
generally contain straight- or branched-chain aliphatic groups generally 
having from 8 to 22 carbon atoms, and optionally also carbocyclic or 
heterocyclic aromatic groups. These radicals are joined to the remaining 
part of the molecule either directly or indirectly, for example by one of 
the following groups: --NHCO--, --NHSO.sub.2 --, --NR--, wherein R 
represents hydrogen or alkyl, --O-- or --S--. The ballast radical may also 
contain water-solubilizing groups, for example sulfo groups or carboxyl 
groups, which may also be present in certain cases in anionic form. Since 
the diffusion properties depend on the molecular size of the complete 
compound used, it suffices in certain cases, for example if the complete 
molecule which is used is large enough, or if the ED precursor compounds 
are worked into the layers in emulsified form using so-called oil formers 
or high-boiling coupler solvents, to use comparatively short chain 
radicals, for example, isoamyl- or tert.-butyl radicals as ballast 
radicals. 
For use in dye diffusion processes for the production of colored transfer 
images, the radicals represented by R.sup.3 and optionally also R.sup.1 
are appropriately to be provided with ballast groups, so that the partly 
colored cleavage products which are produced by alkaline hydrolysis after 
oxidation of the ED compounds also remain in the photographic layer in a 
diffusion-resistant manner. On the other hand, it is advantageous for uses 
of the ED compounds of the present invention for the production of 
so-called retained images to provide only the radical R.sup.1 specifically 
with ballast groups. According to experience, such isatin derivatives of 
the present invention split up after oxidation into non-diffusing, 
substantially colorless ketoaldehydes and into neutral, but deep yellow 
isatins which are diffusible in an alkaline medium. 
An essential advantage of such ED precursor compounds according to the 
present invention is thus also the fact that they do not leave any 
constituents behind after development of the photographic material which 
would impair the image whites of the retained image. 
A few examples of the non-diffusing ED precursor compounds which are used 
according to the present invention are provided in the following: 
______________________________________ 
##STR3## 
Com- 
pound 
No. R.sup.2 R.sup.3 R.sup.4 
______________________________________ 
1 H H H 
2 H H POCH.sub.3 
3 H H PNO.sub.2 
4 CH.sub.3 H H 
5 H 5-Br H 
6 H 5-NO.sub.2 H 
7 H 7-CH.sub.3 H 
8 H H p-OC.sub.14 H.sub.29 
9 H H o-OC.sub.14 H.sub.29 
10 H H o-OC.sub.8 H.sub.17 
11 H H o-OC.sub.10 H.sub.21 
12 H H m-NHCOC.sub.15 H.sub.31 
13 H H p-NHCOC.sub.15 H.sub.31 
14 H 5-Br p-OC.sub.14 H.sub.29 
15 H 5-Br,7-Br p-OC.sub.14 H.sub.29 
16 H 4-CH.sub.3,6-CH.sub.3 
p-OC.sub.14 H.sub.29 
17 H 4-CH.sub.3,5-Cl, 
p-OC.sub.14 H.sub.29 
7-OCH.sub.3 
18 H 5-Br,7-Br o-OC.sub.14 H.sub.29 
19 H H o-OC.sub.12 H.sub.25 
20 H 5-Br,7-Br o-OC.sub.12 H.sub.25 
21 CH.sub.3 H p-OC.sub.14 H.sub.29 
22 CH.sub.3 5-Br,7-Br p-OC.sub.14 H.sub.29 
23 H 5-NHCOC.sub.15 H.sub.31 
H 
24 H 
##STR4## H 
25 H 5-Cl,7-Cl p-OC.sub.14 H.sub.29 
26 H H p-SC.sub.12 H.sub.25 
Compound No. 27 - 
##STR5## 
______________________________________ 
The production of some of the ED-precursor compounds which are used 
according to the present invention will now be described in the following. 
Compound No. 8 
3.7 g of 4-tetradecyloxy-.omega.-bromo-acetophenone (9 mmol) 
were suspended in 
40 ml of dimethylformamide (DMF) 
and stirred with 
1.6 g of isatin (11 mmol) 
and 
0.54 g of sodium carbonate (5 mmol) 
at room temperature. After 31/2 hours, the deposit was suction-filtered and 
washed first of all with methanol, then with water and then with methanol. 
Yield: 1.9 g (=44% of the theoretical yield); 
m.p. 130.degree.-132.degree. C. 
Compound No. 14 
3.9 g of 4-tetradecyloxy-.omega.-bromo-acetophenone (9.5 mmol) 
were suspended in 
35 ml of DMF 
and stirred with 
2.26 g of 5-bromo-isatin (10 mmol) 
and 
0.54 g of sodium carbonate (5 mmol) 
at room temperature. The deposit was suction-filtered after 15 hours and 
washed first of all with methanol, then with water and lastly with 
methanol. The crude product 3.4 g was stirred with hot propanol and 
suction-filtered again. 
Yield: 2.5 g (=47% of the theoretical yield); 
m.p. 141.degree.-142.degree. C. 
Compound No. 15 
This compound was synthetized analogously to compound No. 14, but instead 
of 5-bromo-isatin, 
3.05 g of 5,7-dibromo-isatin (10 mmol) 
were used. 
Yield: 3.2 g (=56% of the theoretical yield); 
m.p. 77.degree.-80.degree. C. 
Compound No. 16 
This compound was synthetized analogously to compound No. 14, but instead 
of 5-bromo-isatin, 
1.75 g of 4,6-dimethylisatin (10 mmol) 
were used. 
Yield: 3.8 g (=84% of the theoretical yield); 
m.p. 151.degree.-153.degree. C. 
Compound No. 17 
This compound was synthetized analogously to compound No. 14, but instead 
of 5-bromo-isatin, 
2.25 g of 5-chloro-7-methoxy-4-methylisatin (10 mmol) 
were used. 
Yield: 1.7 g (=30% of the theoretical yield); 
m.p. 108.degree.-112.degree. C. 
Compound No. 21 
1.9 g of 4-tetradecyloxy-.alpha.-bromo-propiophenone (4.5 mmol) 
were stirred with 
0.7 g of isatin (5 mmol), 
0.27 g of sodium carbonate (2.5 mmol) in 
20 ml of DMF 
for 10 hours at room temperature, then suction-filtered and thereafter 
washed with methanol, water and methanol. 
Yield: 1 g (=87% of the theoretical yield); 
m.p. 125.degree.-127.degree. C. 
##STR6## 
20.25 g of p-aminoacetophenone were dissolved in 100 ml of pyridine and 
mixed drop-wise with stirring with 41.4 g of palmitic acid chloride at 
15.degree. to 20.degree. C. The mixture was further stirred for another 
hour and then poured onto ice/hydrochloric acid. After suction-filtering, 
the mixture was washed with water until neutral and recrystallized from 
methanol while still moist. 
Yield: 49 g; 
m.p. 112.degree.-114.degree. C. 
##STR7## 
4.78 g of acetophenone from stage a were mixed with 2 g of bromine in 80 
ml of glacial acetic acid at from 40.degree. to 50.degree. C. 
After decolorisation and cooling to room temperature, the precipitated 
product was suction-filtered and recrystallised from ethanol. 
Yield: 4.1 g; 
m.p. 119.degree.-121.degree. C. 
c. Compound No. 13 
2.04 g of bromo-acetophenone from experiment b. (4.5 mmol), 
0.8 g of isatin (5.4 mmol), and 
0.27 g of sodium carbonate (2.5 mmol) 
were stirred into 
20 ml of DMF 
for 3 hours at room temperature. 
The mixture was poured into ice water, adjusted to be slightly alkaline 
using sodium carbonate and suction-filtered. It was then washed 
successively with ethanol, water and ethanol and recrystallised from 
ethanol/propanol. 
Yield: 1 g (=43% of the theoretical yield); 
m.p. 157.degree.-161.degree. C. 
The ED precursor compounds according to the present invention are superior 
to the known ED compounds, for example ascorbyl palmitate, and also to the 
known ED precursor compounds insofar as higher maximum color densities may 
be produced simultaneously with lower minimum color densities (fog) with 
these compounds within a given development time. It remains to be seen 
whether the higher maximum color densities which are obtained are to be 
attributed to a ready cleavage (hydrolysis) of the heterocyclic ring and 
thus to a more rapid availability of the actual ED compounds, or to the 
higher reducing power thereof, or to both influences. 
Another advantage of the ED precursor compounds according to the present 
invention is that they are in an oxidation-insensitive form and are only 
converted into the actual ED compounds during development by treatment 
with aqueous alkali (hydrolytic cleavage of the ring). 
The reducible dye-releasers which are used in combination with the ED 
precursor compounds according to the present invention release a 
diffusible dye under alkaline development conditions by reduction or as a 
result of reduction. Reducible dye-releasers are described in the 
following publications: DE-A No. 2,809,716; DE-A No. 3,008,588; DE-A No. 
3,014,669; in EP-A No. 0,004,399 and in GB-A No. 8,012,242. Reducible 
dye-releasers which are more preferably used according to the present 
invention correspond to the following formula II: 
##STR8## 
wherein 
R.sup.1 represents alkyl or aryl; 
R.sup.2 represents alkyl, aryl or a group which, together with R.sup.3, 
completes a condensed ring; 
R.sup.3 represents hydrogen, alkyl, aryl, hydroxyl, halogen such as 
chlorine or bromine, amino, alkylamino, dialkylamino including cyclic 
amino groups (such as piperidino or morpholino), acylamino, alkylthio, 
alkoxy, aroxy, sulfo or a group which, together with R.sup.2, completes a 
condensed ring; 
R.sup.4 represents alkyl; 
R.sup.5 represents alkyl or preferably hydrogen; 
A represents the radical of a diffusible dye or dye precursor; 
X represents a bivalent connecting member of the formula --R--(L).sub.p 
--(R).sub.q --, wherein R represents an alkylene radical having from 1 to 
6 carbon atoms or an optionally substituted arylene or aralkylene radical, 
and the two radicals R may have the same or different meanings; 
L represents --O--, --CO--, --CONR.sup.6 --, --SO.sub.2 NR.sup.6 --, 
--O--CO--NR.sup.6 --, --S--, --SO-- or --SO.sub.2 -- (R.sup.6 =hydrogen or 
alkyl); 
p represents 0 or 1; 
q represents 0 or 1; and 
m represents 0 or 1, 
and at least one of the radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.4 
contains a ballast radical. 
The alkyl radicals represented in formula II by R.sup.1, R.sup.2, R.sup.3 
and R.sup.5 may be straight or branched-chain and usually contain up to 18 
carbon atoms. Examples thereof include methyl, n-propyl, tert.-butyl, 
tetradecyl and octadecyl. The aryl radicals represented by the radicals 
R.sup.1, R.sup.2 and R.sup.3 mentioned are, for example, phenyl groups 
which may be substituted, for example by long-chain alkoxy groups. 
In an acylamino radical represented by R.sup.3, the acyl group is derived 
from aliphatic or aromatic carboxylic acids or sulfonic acids. The 
condensed rings which are completed by R.sup.2 and R.sup.3 are preferably 
carbocyclic rings, for example condensed benzene- or 
bicyclo-[2,2,1]-heptene rings. 
An alkyl radical represented by R.sup.4 may be straight- or branched-chain, 
substituted or unsubstituted and may contain up to 21 carbon atoms. 
Examples include methyl, nitromethyl, phenylmethyl (benzyl), heptyl, 
tridecyl; pentadecyl, heptadecyl and --C.sub.21 H.sub.43. 
Preferred embodiments of the dye-releasers which are used according to the 
present invention are those in which R.sup.1, R.sup.2 and R.sup.3 in a 
quinoid carrier radical together contain not more than 8, in particular 
not more than 5 carbon atoms, and R.sup.4 represents an alkyl radical 
having at least 11 carbon atoms. 
Preferred embodiments are also those in which R.sup.1 represents an 
alkoxyphenyl radical having at least 12 carbon atoms in the alkoxy group 
and R.sup.2, R.sup.3 and R.sup.4 together do not contain more than 8 
carbon atoms. 
The reducible dye-releasers which are preferably used contain, per dye 
radical, one releasable quinoid carrier radical which confers diffusion 
resistance and corresponds to the formula: 
##STR9## 
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are as defined 
above. 
In principle, the radicals of dyes of all dye classes are suitable as dye 
radicals if they are diffusible enough to be able to diffuse through the 
layers of the photosensitive material into the image-receiving layer. For 
this purpose, the dye radicals may be provided with one or more 
alkali-solubilizing groups. The following, inter alia, are suitable as 
alkali-solubilizing groups: carboxyl groups, sulfo groups, sulfonamide 
groups and aromatic hydroxyl groups. Such alkali-solubilizing groups may 
already be preformed in the dye-releasers used according to this 
invention, or may only be produced from the splitting-off action of the 
dye radical from the carrier radical loaded with ballast groups. The 
following are mentioned as dyes which are particularly suitable for the 
present process: azo dyes, azomethine dyes, anthraquinone dyes, 
phthalocyanine dyes, indigoid dyes, triphenylmethane dyes, including those 
dyes which are complexed or may be complexed with metal ions. 
The term "radicals of dye precursors" is understood to mean the radicals of 
such compounds which are converted into dyes during photographic 
processing by conventional or additional processing steps, whether by 
oxidation or by coupling, by complex formation or by exposing an 
auxochromic group in a chromophoric system, for example by saponification. 
Dye precursors in this context may be leuko dyes, couplers or dyes which 
are converted into other dyes during processing. As far as a 
differentiation between dye radicals and the radicals of dye precursors is 
not of paramount importance, the latter should also be understood 
hereinafter under the term "dye radicals". 
In a preferred embodiment of the present invention, the color-photographic 
recording material in monochomatic processes contains at least one 
image-producing layer unit, and in processes for the production of 
multicolored images, the colour-photographic recording material usually 
contains at least three image-producing layer units, each of which 
contains at least one photosensitive silver halide emulsion layer and a 
combination associated with this layer of a non-diffusing, reducible 
color-providing compound and an electron donor compound, one ED precursor 
compound according to the present invention being used in at least one 
layer unit. One of the layer units is usually predominantly sensitive to 
blue light, another layer unit is predominantly sensitive to green light 
and a third unit predominantly sensitive to red light, the associated 
color-providing compounds in each case providing complementary-colored 
image dyes. 
The terms "association" and "associated" are understood to mean that the 
mutual arrangement of silver halide emulsions, ED compound or ED precursor 
compound and dye-releaser is such that an interaction is possible between 
them which allows an image-wise conformity between the silver image which 
has formed and the consumption of ED compound on the one hand and between 
the unconsumed ED compound and the dye-releaser on the other hand, so that 
in conformity with the undeveloped silver halide, an image-wise 
distribution of diffusible dye is produced. For this purpose, the 
photosensitive silver halide and the combination of dye-releaser and ED 
compound do not necessarily have to be in the same layer. They may also be 
accommodated in adjacent layers which in each case belong to the same 
layer unit. 
In order to ensure an adequate interaction between the dye-releaser and the 
associated ED precursor compound, it is advisable to accommodate both 
these compounds of one combination in the same layer which, however, does 
not have to be identical to the associated silver halide emulsion layer. 
The fact that the ED precursor compounds according to the present 
invention are stable to hydrolysis under neutral conditions, and thus are 
also oxidation-insensitive, means that these compounds are particularly 
suitable for use in a common emulsion (together with the dye-releaser), 
while conventional ED compounds have too high an oxidation sensitivity 
under comparable conditions, so that they cannot be used in the same 
emulsion with the dye-releasers. 
All methods by which hydrophobic compounds are usually worked into 
photographic layers are suitable for working in the ED precursor compounds 
of the present invention, i.e., the conventional emulsifying techniques 
are included, for example methods by which photographic auxiliaries are 
added to the casting solutions in the form of emulsifiers using so-called 
oil formers. During this process, all methods which necessitate the use of 
alkali should appropriately be avoided. 
The reducible dye-releaser is usually used in a layer in a sufficient 
quantity for producing a color image having as high a maximum color 
density as possible, for example in a quantity of from 1 to 
20.times.10.sup.-4 mol/m.sup.2. The quantity of ED precursor compound 
according to this invention is adapted to the quantity of dye-releaser. It 
should be sufficient in order to achieve as high a maximum color density 
as possible, i.e., to be able to cause as complete a reduction of the 
dye-releaser as possible. On the other hand, it should not be 
substantially higher than required for this purpose, so that the reducing 
agent produced therefrom may be consumed as completely as possible by the 
development of the exposed silver halide in the exposed areas. The 
quantity ratios which are most favourable in each individual case between 
silver halide, ED precursor compound and dye-releaser are appropriately 
determined by routine experiments. Reliable results may be obtained, for 
example, when the ED precursor compound is present in each case in from 
0.5 to 5 times the molar quantity, based on the dye-releaser. The suitable 
quantity ratio between silver halide and the associated dye-releaser 
approximately ranges from 2 to 20 mols of silver halide per mol of 
dye-releaser. 
Intermediate layers are appropriately present between different layer units 
and they may contain compounds which are capable of reacting with 
diffusing development products and are capable of stopping the diffusion 
thereof from one layer unit into another. This contributes to the fact 
that the association remains restricted in each case to one layer unit. 
Compounds of this type are known. For example, non-diffusing hydroquinone 
derivatives and, for example, the "scavenger compounds" described in the 
publication "Research Disclosure No. 17,842" (February 1971) are suitable 
for this purpose. Last but not least, the ED precursor compounds according 
to this invention may also take over this function, that is, independently 
of the type of color-providing compound which is used (color coupler, 
dye-releaser), if the ED precursor compounds of the present invention are 
embedded as so-called scavengers in an intermediate layer between 
different layer units. 
The interaction between the exposed silver halide and the ED compound is 
generally caused by the oxidized form of the silver halide developing 
agent which is used. The latter is oxidized image-wise during development 
and the oxidation product is, for its part, capable of oxidizing the ED 
compound and thus of withdrawing from the reaction with the dye-releaser. 
The following, for example, are included as silver halide developing 
agents: hydroquinone and derivatives thereof, catechol and derivatives 
thereof, p-phenylenediamine derivatives and 3-pyrazolidone compounds, in 
particular 1-phenyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 
4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone, 
1-phenyl-4-methyl-3-pyrazolidone, 1-phenyl-5-methyl-3-pyrazolidone, 
1-phenyl-4,4-bis-(hydroxymethyl)-3-pyrazolidone, 
1,4-dimethyl-3-pyrazolidone, 4-methyl-3-pyrazolidone, 
4,4-dimethyl-3-pyrazolidone, 1-(3-chlorophenyl)-4-methyl-3-pyrazolidone, 
1-(4-chlorophenyl)-4-methyl-3-pyrazolidone, 
1-(3-chlorophenyl)-3-pyrazolidone, 1-(4-chlorophenyl)-3-pyrazolidone, 
1-(4-tolyl)-4-methyl-3-pyrazolidone, 
1-(4-tolyl)-4-hydroxymethyl-4-methyl-3-pyrazolidone, 
1-(3-tolyl)-3-pyrazolidone, 1-(3-tolyl)-4,4-dimethyl-3-pyrazolidone, 
1-(2-trifluoroethyl)-4,4-dimethyl-3-pyrazolidone and 
5-methyl-3-pyrazolidone, including those derivatives of 3-pyrazolidone 
which are present in masked form, for example acetylated phenidone 
derivatives. 
A combination of different silver halide developing agents may also be 
used. The silver halide developing agents may be contained in an alkaline 
developer preparation or may be completely or partly contained in one or 
more layers of the color-photographic recording material to be processed. 
In order to carry out the dye diffusion transfer process according to the 
present invention, a photosensitive element is usually used which contains 
one or more silver halide emulsion layer units and the reducible 
dye-releasers associated therewith and ED compounds or precursors thereof, 
and an image-receiving element is usually used, in which the required 
color image is produced by the image-wise transfer of the released dyes. 
For this purpose, there must be a firm contact between the photosensitive 
element and the image-receiving element at least during a finite period of 
time within the developing time, so that the image-wise distribution of 
diffusing dyes which is produced in the photosensitive element as a result 
of development may be transferred onto the image-receiving element. The 
content may be produced after development has been started, or it may 
already have been produced before development starts. The latter is the 
case, for example, if a so-called integral recording material is used for 
carrying out the dye diffusion transfer process, in which material the 
photosensitive element and the image-receiving element form an integral 
unit, also termed hereinafter a "monosheet material", which may still 
exist at the end of the development procedure, even if the photosensitive 
element is not separated from the image-receiving element even after the 
color transfer has been completed. An embodiment of this type is 
described, for example, in DE-A No. 2,019,430. 
Accordingly, the image-receiving element may be a component of the 
color-photographic recording material, for example in the form of an 
image-receiving layer which is positioned on a transparent substrate below 
the photosensitive element, a light-impermeable, preferably a 
light-reflecting, binder layer appropriately being located between the 
image-receiving layer and the photosensitive element. The image-receiving 
layer which, in another form of the color transfer process may, however, 
also be positioned on a separate substrate (image-receiving sheet), 
usually contains in a known manner a basic mordant for diffusible anionic 
(acid) dyes. 
Long-chain quaternary ammonium or phosphonium compounds or tertiary 
sulfonium compounds, for example those compounds which are described in 
US-A Pat. No. 3,271,147 and US-A Pat. No. 3,271,148, are preferably used 
as mordants for acid dyes. Furthermore, certain metal salts and hydroxides 
thereof which form sparingly soluble compounds with the acid dyes may also 
be used. The dye mordants are dispersed in the receiving layer in a 
conventional hydrophilic binder, for example in gelatine, polyvinyl 
pyrrolidone, or completely or partially hydrolysed cellulose esters. Of 
course, some binders may also function as mordants, for example mixed 
polymers or polymer mixtures of vinyl alcohol and N-vinylpyrrolidone, as 
described, for example, in DE-B No. 1,130,284, also those which are 
polymers of nitrogen-containing quaternary bases, for example polymers of 
N-methyl-2-vinylpyridine, as described, for example, in US-A Pat. No. 
2,484,430. Other mordanting binders which may be used include, for 
example, guanylhydrazone derivatives of alkyl vinylketone polymers, as 
described in US-A Pat. No. 2,882,156, or guanylhydrazone derivatives of 
acylstyrene polymers, as described, for example, in DE-A No. 2,009,498. 
However, other binders, for example gelatine are generally also added to 
the last-mentioned mordanting binders. Other polymeric mordants are 
described, for example in US-A Pat. No. 3,709,690 and in DE-A No. 
2,315,304; DE-A No. 2,445,782; DE-A No. 2,551,786 and DE-A No. 2,631,521. 
Moreover, the color-photographic recording material according to the 
present invention may also contain acid layers and so-called retarding or 
delaying layers which together form a so-called integral neutralisation 
system. An integral neutralisation system of this type may be positioned 
in a known manner between the substrate and the image-receiving layer 
positioned thereon, or at another point in the laminated structure, for 
example above the photosensitive layers, i.e., on the other side of these 
photosensitive layers, seen from the image-receiving layer. The 
neutralisation system is usually oriented such that the retarding or 
delaying layer is positioned between the acid layer and the point at which 
an alkaline developing liquid or developing paste is applied. Such acid 
layers, retarding layers etc., from both existing neutralisation systems 
are known, for example, from US-A Pat. No. 2,355,030; US-A Pat. No. 
2,983,606; US-A Pat. No. 3,362,819; US-A Pat. No. 3,362,821 and from DE-A 
No. 2,455,762; DE-A No. 2,601,653; DE-A No. 2,716,505 and DE-A No. 
2,816,878. A neutralisation system of this type may also contain in a 
known manner two or more retarding layers. 
Moreover, in a particular embodiment, the recording material according to 
the present invention may contain one or more pigmented, opaque layers 
which are permeable to aqueous liquids. These layers may fulfil two 
functions: On the one hand, the layers may prevent the undesired entry of 
light into photosensitive layers, and on the other hand, a pigment layer 
of this type, in particular if a light or white pigment, for example 
TiO.sub.2, is used, may form an aesthetically pleasant background for the 
color image which is produced. Integral color-photographic recording 
materials having a pigment layer of this type are known, for example from 
US-A Pat. No. 2,543,181 and from DE-B No. 1,924,430. Instead of a 
preformed opaque layer, means may also be provided to produce such a layer 
only during the course of the development process. Corresponding to the 
two functions mentioned, pigment layers of this type may comprise two or 
more partial layers, one of which contains a white pigment, for example, 
and the other contains, for example, a dark, light-absorbing pigment, for 
example carbon black. 
In a particularly preferred embodiment of the present invention, the 
photographic material is an integral color-photographic recording material 
for carrying out the dye diffusion transfer process and it has, for 
example, the following layer elements: 
(1) a transparent substrate, 
(2) an image-receiving layer, 
(3) a light-reflecting layer, 
(4) a photosensitive element with at least one photosensitive silver halide 
emulsion layer and a combination associated with this layer of reducible 
dye-releaser and ED precursor compound, 
(5) a retarding layer, 
(6) an acid polymer layer, and 
(7) a transparent substrate. 
The monosheet material may be assembled such that two different parts are 
produced separately from each other, namely the photosensitive part (layer 
elements 1 to 4) and the cover sheet (layer elements 5 to 7) which are 
then positioned one on top of the other on the layer side and are joined 
together, optionally using spacing strips, so that a space is formed 
between the two parts for receiving an exactly measured quantity of a 
developer preparation. The layer elements 5 and 6 which together form the 
neutralisation system may also be positioned between the substrate and the 
image-receiving layer of the photosensitive part, but in the reverse 
order. 
Furthermore, means may also be provided for introducing a developer 
preparation between the photosensitive part and the cover sheet, for 
example in the form of a rupturable container which is positioned on the 
side and discharges its contents between two adjacent layers of the 
monosheet material under the influence of mechanical force. 
In addition to aqueous alkali, the developer preparation may also contain 
developer compounds which, however, must be co-ordinated with the type of 
dye-producing compounds. Other possible components of the developer 
preparation include thickening agents to increase the viscosity, for 
example hydroxyethyl cellulose, silver halide solvents, for example sodium 
thiosulphate, or one of the bis-sulfonyl alkane compounds described in 
DE-A No. 2,126,661, and opacifiers to produce opaque layers, for example 
pigments of TiO.sub.2, ZnO, barium sulphate, barium stearate or kaolin. 
Some of these components may alternatively or additionally be embedded in 
one or more layers of the color-photographic recording material of the 
present invention.

EXAMPLE 1 
A mordant layer, a light-reflecting layer and a photosensitive silver 
halide emulsion layer were applied in the following sequence to a 
transparent substrate of cellulose triacetate: 
Mordant layer 
3.75 g of a copolymer of 1 part of styrene and 1 part of maleic acid imide 
of N,N-dimethyl-N-hexadecyl-N- -amino-propyl-ammonium bromide were 
dissolved in 15 ml of ethanol, and this solution was stirred into 75 ml of 
a 5% gelatine solution and homogenised. After adding 2.6 ml of a 5% 
saponin solution and 1 ml of a 2% aqueous mucochloric acid solution, the 
mixture was adjusted to a conventional casting viscosity (about 11 mPa.s), 
and the solution was applied to the substrate at 40.degree. C. by the dip 
process (casting rate 5 m/min). 
Light-reflecting layer 
A suspension of 42 g of TiO.sub.2 in 20 ml of water was dispersed in 150 ml 
of an 8% aqueous gelatine solution with the addition of 5 ml of a 5% 
aqueous solution of sodium dodecyl benzene sulfonate and 5 ml of 5% 
aqueous saponin solution. After adding 1 ml of a 2% mucochloric acid 
solution, the dispersion was adjusted to a viscosity of 13 mPa.s at 
40.degree. C., and was applied to the dried mordant layer by the dip 
process (casting rate 5 m/min). 
Silver halide emulsion layer 
1 mmol of one of the dye-releasers specified in the following and 1.5 mmol 
of one of the ED precursor compounds also specified in the following were 
dissolved in 5 ml of ethyl acetate and, after adding 2 ml of palmitic acid 
diethylamide, were emulsified in a Buhler homogeniser at about 1,000 
r.p.m. into 25 ml of a 5% gelatine solution with the addition of 5 ml of a 
5% aqueous solution of sodium-dodecylbenzene sulfonate. The emulsion was 
filtered over a folded filter, and made up to 75 ml with 5% gelatine 
solution. 
After adding 1 ml of a 2% mucochloric acid solution, the emulsiom was mixed 
with 32 g of a ready-for-casting silver bromo-iodide emulsion. This 
emulsion was produced using 74 g of AgNO.sub.3 /kg of emulsion. It had an 
Ag/gelatine ratio of 1:1.1. The silver bromide emulsion contained 0.67 mol 
% of silver iodide. 
The mixtures were applied to the previously described support by the dip 
process at a rate of 5 m/min at about 40.degree. C. 
After drying for 24 hours, the different samples were exposed on the 
emulsion side through grey step filter and were developed for 4 minutes at 
18.degree. C. using a developer paste which was applied in a thickness of 
about 300 .mu.m and was composed as described in the following, were 
stopped for 2 minutes in a 5% acetic acid solution, and then briefly 
rinsed and dried. 
Developer 
20 g of carbethoxymethyl cellulose were dissolved with stirring in 800 ml 
of water. 
40 g of solid NaOH, 
1.5 g of ethylenediamine-tetra-acetic acid-sodium salt, 
11.5 g of borax, 
1 g of sodium hexametaphosphate, 
3 g of KBr, 
1.6 g of 1-phenyl-4-methyl-4-oxymethyl-pyrazolidone-3, and 
0.1 g of 1-phenyl-5-mercaptotetrazole 
were added to the homogeneous solution. 
The solution was made up to 1000 ml with water, and the pH was then 
adjusted to 13.2 to 13.3 by adding 30 ml of glacial acetic acid. 
The following dye-releasers A, B and C were used for the following 
experiments. 
##STR10## 
A compound corresponding to the following formula was used as a known ED 
precursor compound for comparison (EP-A No. 0,034,749, compound 4): 
##STR11## 
The following combinations were tested for the D.sub.min /D.sub.max values 
which may be achieved: 
______________________________________ 
Dye ED compound D.sub.min 
D.sub.max 
______________________________________ 
A D 0.46 1.92 
8 0.16 1.82 
14 0.02 1.56 
15 0.02 1.80 
18 0.02 0.98 
B D 0.16 1.86 
8 0.06 1.76 
15 0.03 1.56 
C D 0.18 1.93 
8 0.11 1.90 
15 0.06 1.93 
______________________________________ 
EXAMPLE 2 
(not according to the present invention) 
A photosensitive element of a photographic recording material was produced 
by successively applying the following layers to a transparent substrate 
consisting of polyethylene terephthalate. The quantities relate in each 
case to one square meter. 
1. Green-sensitized AgBr-negative emulsion layer consisting of 0.55 g of 
AgNO.sub.3, containing 0.17 g of dye-releaser C (compound releasing 
magenta dye), 0.12 g of ED precursor compound E (compound according to 
Research Disclosure 19507, July 1980), 0.29 g of diethyllauramide and 1 g 
of gelatine. 
2. Protective layer containing 0.05 g of 
2-isooctadecyl-5-sulfohydroquinone, 0.74 g of acetylation product of 
4-methylphenidone, 0.47 g of palmitic acid diethylamide and 2 g of 
gelatine. 
3. Opaque light-reflecting layer containing 13.45 g of TiO.sub.2 and 2 g of 
gelatine. 
4. Protective layer containing 3.85 g of gelatine and 0.20 g of diisooctyl 
hydroquinone. 
5. Image-receiving layer containing 2.5 g of a polymeric mordant of 
4,4'-diphenylmethane-diisocyanate and N-ethyldiethanolamine, quaternised 
with epichlorohydrin according to DE-A No. 2,631,521, Example 1, and 6.25 
g of gelatine. 
6. Protective and hardening layer containing 0.9 g of compound F (hardening 
agent) and 0.6 g of gelatine. 
The recording material was exposed through the transparent substrate behind 
a conventional grey wedge and was developed in an open tray at 22.degree. 
C. for 15 minutes in a bath having the following composition: 
921 g of H.sub.2 O 
25 g of 2-methyl-2-propyl-1,3-propanediol, 
20 g of 1,4-cyclohexanedimethanol 50%, 
3 g of KBr, and 
40 g of KOH. 
The material was then rinsed for 5 minutes and was dried. 
EXAMPLES 3 AND 4 
(according to the present invention) 
The process was carried out as stated in Example 2, but instead of the 
photosensitive element described in Example 2, such elements were used 
which contained the ED precursor compounds Nos. 8 and 26 according to the 
present invention, instead of ED precursor compound E in layer 1, in the 
same molar quantity. 
The recording materials obtained according to Examples 2, 3 and 4 produced 
positive magenta transfer images having the following D.sub.min /D.sub.max 
values: 
______________________________________ 
ED compound D.sub.min 
D.sub.max 
______________________________________ 
E 0.10 0.68 
8 0.12 1.57 
26 0.13 1.50 
______________________________________ 
EXAMPLE 5 
The kinetics of the dye formation were investigated for ED precursor 
compound E (comparison) and for ED precursor compounds Nos. 8 and 26 
according to the present invention by measuring, for each of the materials 
to be tested, the color density produced in the image-receiving layer 
depending on the development time and by representing the values as a 
curve. FIG. 1 represents the color density (ordinate) as a function of the 
development time (abscissa) for ED precursor compound 1 (curve 1), and for 
ED precursor compound 8 (curve 2) and for ED precursor compound 26 (curve 
3) of the present invention. It may be seen that the compounds according 
to the present invention are clearly more active, i.e., they produce 
clearly higher color transfers, particularly with shorter development 
times. 
EXAMPLE 6 
A photosensitive element of a photographic recording material according to 
the present invention was produced by successively applying the following 
layers to a transparent substrate consisting of polyethylene 
terephthalate. The quantities relate in each case to one square meter. 
1. Blue-sensitized AgBr-negative emulsion layer consisting of 0.76 g of 
AgNO.sub.3, containing 0.29 g of dye-releaser G (compound releasing yellow 
dye), 0.23 g of ED precursor compound No. 8 0.52 g of palmitic acid 
diethylamide and 1.5 g of gelatine. 
2. Yellow filter layer containing 0.16 g of yellow dye Solvent Yellow 29 
(C.I. 21230), 0.05 g of 2-iso-octadecyl-5-sulfo-hydroquinone and 1.0 g of 
gelatine. 
3. Green-sensitized AgBr negative emulsion layer consisting of 0.55 g of 
AgNO.sub.3, containing 0.17 g of dye resistor C (compound releasing 
magenta dye), 0.11 g of ED precursor compound No. 8, 0.28 g of 
diethyllauramide and 1 g of gelatine. 
4. Intermediate layer containing 0.07 g of 
2-isooctadecyl-5-sulfo-hydroquinone, 0.47 g of acetylation product of 
4-methyl-1-phenylpyrazolidone-(3) (developer) and 2 g of gelatine. 
5. Red-sensitized AgBr-negative emulsion layer consisting of 0.5 g of 
AgNO.sub.3, containing 0.20 g of dye releaser H (compound releasing cyan 
dye), 0.10 g of ED precursor compound No. 8, 0.30 g of palmitic acid 
diethylamide and 1.14 g of gelatine. 
6. Protective layer containing 0.05 g of acetylation product of 
4-methyl-1-phenylpyrazolidone-(3) and 0.63 g of gelatine. 
7. Opaque light-reflecting layer containing 13.45 g of TiO.sub.2 and 20 g 
of gelatine. 
8. Protective layer containing 3.85 g of gelatine and 0.2 g of 
diisoctylhydroquinone. 
9. Image-receiving layer containing 2.53 g of a polymeric mordant 
consisting of 4,4'-diphenylmethane diisocyanate and N-ethyldiethanolamine, 
quaternised with epichlorohydrin according to DE-A No. 2,631,521, Example 
1, and 6.34 g of gelatine. 
10. Protective and hardening layer containing 0.9 g of compound F 
(hardening agent) and 0.6 g of gelatine. 
The recording material thus produced was exposed and developed as in 
Example 2. After rinsing and drying, the positive multicolored transfer 
image produced the following D.sub.min and D.sub.max values: 
______________________________________ 
B G R 
______________________________________ 
D.sub.min 
0.19 0.19 0.18 
D.sub.max 
1.95 1.88 2.15 
______________________________________ 
EXAMPLE 7 
The process was carried out as stated in Example 6, but 0.31 g of dye 
releaser J were used instead of dye-releaser G in layer 1, and 0.25 g of 
dye-releaser K were used instead of dye-releaser C in layer 3. The 
recording material thus produced was exposed and developed as in Example 
2. 
The positive multicolored transfer image produced the following D.sub.min 
and D.sub.max values: 
______________________________________ 
B G R 
______________________________________ 
D.sub.min 
0.20 0.19 0.18 
D.sub.max 
2.20 2.02 2.08 
______________________________________ 
In FIG. 2, the color density produced in the image-receiving layer 
depending on the development time is measured and represented as a curve 
(curve 1-blue filter; curve 2-green filter; curve 3-red filter). The image 
formation rate of all three colors is almost the same and development is 
almost completed after about one minute. 
Formulae relating to Example 2 to 7 
##STR12##