Heat development process and color photographic recording material suitable for this process

Compounds corresponding to formula I are suitable for use as thermal development and diffusion promoting agents for the heat development process. The said compounds enable higher color transfer densities to be obtained and/or the development time to be reduced. ##STR1## wherein R.sup.1, R.sup.2 denote alkyl, cycloalkyl, aralkyl, aryl or acyl and PA0 Z denotes a group for completing a saturated heterocyclic ring containing 5 to 11 ring members.

This invention relates to a heat development process in which an imagewise 
exposed colour photographic recording material containing a layer of 
binder with silver halide and at least one colour producing compound on a 
common layer support is subjected to development by heat treatment in 
contact with an image receptor layer which may be an integral component of 
the recording material or may be arranged on a separate layer support, at 
least one so-called thermal development and diffusion-promoting agent 
being present. 
It is known to produce colour images by heat treatment by means of suitable 
colour photographic recording materials. Particularly suitable colour 
producing compounds are those which can be incorporated in a 
non-diffusible form in the layer of a photographic recording material and 
are capable of releasing a diffusible dye (dye releasing compounds) as a 
result of development. 
The particular suitability of such dye releasing compounds is due to the 
ability of the dyes which have been released imagewise to be transferred 
to special image receptor layers to form a brilliant colour image which 
has no image silver or silver halide superimposed on it and therefore 
requires no after-treatment. The combination of a heat development Process 
with dye diffusion process thus provides an advantageous rapid process for 
the production of colour images. A recording material suitable for this 
purpose has been described, for example, in DE-A No. 3 215 485. 
According to the aforesaid publication, a recording material having a layer 
which contains a combination of silver halide, silver benzotriazole, a dye 
releasing compound and guanidine trichloroacetate (base donor) is exposed 
imagewise and then subjected to a heat treatment in contact with an image 
receptor sheet, and the dye which is released imagewise is transferred to 
the image receptor sheet. For the production of multicoloured images it is 
necessary to provide several such combinations and the silver halide in 
each of these combinations is sensitive to a different spectral region of 
light and according to its particular spectral sensitivity is associated 
with a particular dye releasing compound capable of releasing a dye of a 
different colour, in most cases a dye which is complementary to the colour 
of the light to which the particular silver halide is predominantly 
sensitive. Such associations may be arranged one above the other in 
different layers. 
It is known to carry out the heat development process in the presence of 
suitable compounds, so-called melt formers or thermal solvents as 
described, for example, in RESEARCH DISCLOSURE Publications No. 15 027 
(October 1976), No. 15 108 (November 1976) and No. 17 029 (June 1978) or 
in DE-A No. 3 339 810, EP-A No. 0 119 615 or EP-A No. 0 122 512. The above 
mentioned compounds are generally solid under normal conditions but molten 
at the elevated temperatures of heat treatment and promote the development 
processes by virtue of their dipolar character. The so-called thermal 
solvents are generally compounds having a protic character. Although heat 
treatment may be carried out dry when the aforesaid thermal solvents are 
used, i.e. without moistening the recording materials or the image 
receptor sheets, and satisfactory results can be obtained under these 
conditions, it is desired to obtain a further improvement to this process 
so as to reduce the time required for treatment and/or achieve higher 
colour transfer densities. 
The present invention relates to a heat development process for the 
production of colour images, in which an imagewise exposed colour 
photographic recording material having at least one layer of binder which 
is arranged on a layer support and contains light-sensitive silver halide, 
optionally in combination with a substantially light-insensitive silver 
salt, and at least one non-diffusible, colour producing compound capable 
of releasing a diffusible dye as a result of development, is developed by 
heat treatment in the presence of a thermal development and diffusion 
promoting agent, the dye which is released imagewise from the 
non-diffusible colour producing compound being transferred to an image 
receptor layer which is capable of absorbing diffusible dyes, 
characterised in that the thermal development and diffusion promoting 
agent corresponds to the following formula I 
##STR2## 
wherein R.sup.1,R.sup.2 denote alkyl, cycloalkyl, aralkyl, aryl or acyl 
and 
Z denotes a group for completing a saturated heterocyclic ring having 5 to 
11 ring members. 
The invention also relates to a colour photographic recording material 
which is suitable for the heat development process and contains at least 
one thermal development and diffusion-promoting agent of the type 
indicated in at least one of its layers. 
R.sup.1 and R.sup.2 may be identical or different. Together they have at 
least two carbon atoms and not more than 20 carbon atoms, preferably not 
more than 8 carbon atoms. 
An alkyl group represented by R.sup.1 or R.sup.2 may be straight chained or 
branched and may be substituted and preferably contains 1 to 4 carbon 
atoms. Examples include methyl. ethyl, propyl, isopropyl, n-butyl, 
s-butyl, methoxymethyl, cyclohexylmethyl and hydroxyethyl. Cyclohexyl is 
an example of a cycloalkyl group represented by R.sup.1 or R.sup.2. Benzyl 
is an example of an aralkyl group represented by R.sup.1 and R.sup.2. The 
aryl group represented by R.sup.1 or R.sup.2 may be, for example, phenyl, 
tolyl, methoxyphenyl or N-methyl-N-acetylamino-phenyl. 
An acyl group represented by R.sup.1 or R.sup.2 may be derived from 
aliphatic or aromatic carboxylic or sulphonic acids or from carbamic or 
sulphamic acids. Acetyl and methylsulphonyl are examples. 
The group Z for completing a heterocyclic ring may in particular be an 
alkylene group containing at least 2 carbon atoms and preferably not more 
than 10 carbon atoms, and the ring formed with the urea group preferably 
has 5 to 7 ring members. Such an alkylene group may be straight chained or 
branched and may be substituted by hydroxyl, cycloalkyl, aryl or 
heterocyclic groups. 
Z is preferably an alkylene group having the structure 
##STR3## 
wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 may denote, independently of 
one another, hydrogen or an alkyl group with up to 6 carbon atoms, 
preferably methyl or ethyl, and 
1 and m may have the value 0, 1 or 2 but they cannot both be 0. 
The thermal development and diffusion promoting agents according to the 
invention (hereinafter denoted by the acronym TEDM=thermisches 
Entwicklungs- und Diffusionsforderungsmittel) evidently act as a solvating 
medium under the conditions of heat development to assist the ongoing 
reactions such as development of the silver halide or of the organic 
silver salt under the influence of a reducing agent, release of the 
diffusible dyes from the colour producing compounds and diffusion of the 
dyes into an image receptor layer. By suitable variation of substituents 
R.sup.1 to R.sup.6, in particular of the substituents R.sup.1 and R.sup.2, 
the solvent properties of the TEDM according to the invention can be 
influenced as desired to render them more hydrophilic or more hydrophobic. 
Suitable examples of the thermal development and diffusion-promoting agents 
(TEDM) according to the invention are shown below: 
##STR4## 
Particularly preferred examples of the TEDM according to the invention, 
such as compounds 1 and 15, are cyclic N,N'-dialkylureas which have been 
described, for example, in the literature under the chemical acronym DMPU 
(=dimethylpropylene-urea) or DMEU (=dimethyl-ethylene-urea). 
DMPU has in most recent times been found in organic chemistry to be a 
solvent equivalent to HMPTA (=hexamethylphosphoric acid triamide). There 
is the further very important advantage that cyclic ureas are 
physiologically harmless(as confirmed for DMPU, for example, in Nachr. 
chem. Techn. Lab. 33 (1985), No.5, 396). 
The accessibility of cyclic ureas and their preliminary stages is known. 
Some literature references are given below. 
Boon, Chem. Soc. 1947, 307, 315; U.S. Pat. No. 2,422,400 (1944): Marstell, 
Frost, J.Amer.Chem.Soc. 72 [1950], 1032; U.S. Pat. No. 2,847,418 (1955); 
Hall, Schneider, J.Amer.Chem.Soc. 80 [1958], 6409, 6412; Kirkewool, 
Wright, J.Amer.Chem.Soc. 76 [1954] 1836, 1839); U.S. Pat. No. 2,398,284 
[1943]: U.S. Pat. No. 2,373,136. 
The TEDM of an aprotic type used according to the invention are 
predominantly liquid under normal conditions (and in this respect differs 
from the previously known thermal solvents, which are solid at normal 
temperature) and by virtue of their high solubility in water may in most 
cases be added directly, either without dilution or as aqueous solutions, 
to the casting solutions for light-sensitive or light-insensitive layers. 
If a TEDM is insoluble in water, it may be introduced in the form of 
dispersions. These may be dispersions of the pure substances or 
dispersions of solutions of the pure substances in a high boiling organic 
solvent (=oil former). 
The quantity put into the process may vary within a wide range and depends 
inter alia on whether the compounds are distributed over several or all of 
the layers of the recording material according to the invention or 
concentrated in a particular layer. The quantity required per square metre 
also depends, of course, on the quantity of binder used. The man in the 
art can easily determine suitable concentrations by simple, routine tests. 
Based on the quantity of binder, the substances may be used at 
concentrations of 2 to 100% by weight but are preferably used at 
concentrations of 20 to 50% by weight. Overdosing with TEDM generally 
results in too dense a colour fog (D.sub.min). 
A colour photographic recording material suitable for carrying out the heat 
development process according to the invention contains, on a 
dimensionally stable layer support, at least one layer of binder 
containing a light-sensitive silver halide, optionally in combination with 
a substantially light-insensitive silver salt and a non-diffusible colour 
producing compound which is capable of producing a diffusible dye as a 
result of heat development, and the colour photographic recording material 
in addition contains, in one of its layers, one or more of the thermal 
development and diffusion promoting agents (TEDM) according to the 
invention. 
An essential constituent of the heat developable recording material 
according to the present invention is the silver halide, which may consist 
of silver chloride, silver bromide, silver iodide or mixtures thereof 
having a particle size of from 0.01 to 2.0 .mu.m, preferably from 0.1 to 
1.0 .mu.m. It may be present in the form of unsensitized silver halide or 
it may be chemically and/or spectrally sensitized by suitable additives. 
The quantity of light-sensitive silver halide in the particular layer may 
range from 0.01 to 2.0 g per m.sup.2 but owing to its catalytic function 
(as exposed silver halide) the actual quantity of silver halide used in 
some embodiments lies mainly in the lower part of the given range. 
The silver salt which is substantially insensitive to light may be, for 
example, one which is comparatively stable in the presence of light, e.g. 
an organic silver salt. Suitable examples of such salts include the silver 
salts of aliphatic and aromatic carboxylic acids and the silver salts of 
heterocyclic compounds containing nitrogen as well as the silver salts of 
organic mercapto compounds. 
The following are preferred examples of silver salts of aliphatic 
carboxylic acids: Silver behenate, silver stearate, silver oleate, silver 
laurate, silver caprate, silver myristate, silver palmitate, silver 
maleate, silver fumarate, silver tartrate, silver furoate, silver 
linolate, silver adipate, silver sebacate, silver succinate, silver 
acetate and silver butyrate. The carboxylic acids of these silver salts 
may be substituted, for example by halogen atoms, hydroxyl groups or 
thioether groups. 
The following are examples of silver salts of aromatic carboxylic acids and 
other compounds containing carboxyl groups: Silver benzoate, 
silver-3,5-dihydroxybenzoate, silver-o-methylbenzoate, 
silver-m-methylbenzoate, silver-p-methylbenzoate, 
silver-2,4-dichlorobenzoate, silver acetamidobenzoate, silver gallate, 
silver tannate, silver phthalate, silver terephthalate, silver salicylate, 
silver phenylacetate, silver pyromellitate, silver salts of 
3-carboxymethyl-4-methyl-4-thiazoline-2-thione and similar heterocyclic 
compounds. Silver salts of organic mercaptans are also suitable, e.g. the 
silver salts of 3-mercapto-4-phenyl-1,2,4-triazole, 
2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 
2-mercaptooctadiazole, mercaptotriazine and of thioglycollic acid as well 
as the silver salts of dithiocarboxylic acids, e.g. of dithioacetic acid. 
The silver salts of compounds containing an imino group are also suitable. 
Preferred examples of these compounds include the silver salts of 
benzothiazole and its derivatives, e.g. silver salts of alkyl- and/or 
halogensubstituted benzotriazoles such as the silver salts of 
methyl-benzotriazole and 5-chlorobenzotriazole, as well as the silver 
salts of 1,2,4-triazole, 1-H-tetrazole, carbazole and saccharine and the 
silver salts of imidazole and its derivatives. 
The quantity of substantially light-insensitive silver salts to be applied 
according to the invention is in the range of 0.05 to 5 g per m.sup.2 in 
the particular layer in which it is used. The substantially 
light-insensitive silver salt and the light-sensitive silver halide may be 
present side by side as separate particles or they may be present in a 
combined form which may be produced, for example, by treating a 
substantially light-insensitive silver salt in the presence of halide ions 
so that light-sensitive centres of light-sensitive silver halide form on 
the surface of the particles of substantially light-insensitive silver 
salt by a process of double conversion, see U.S. Pat. No. 3,457,075. 
The substantially light-insensitive silver salt serves as a reservoir for 
metal ions which are reduced to elementary silver under the catalytic 
influence of imagewise exposed silver halide when heat development takes 
place in the presence of a reducing agent, and act as oxidizing agents 
(for the reducing agent present) under these conditions. 
Another essential component of the recording material according to the 
invention is the non-diffusible colour producing compound which is capable 
of releasing a diffusible dye by a redox reaction in the course of 
development and which will hereinafter be referred to as dye releasing 
compound. 
The dye releasing compounds used according to the invention may be any one 
of the different types of compounds which are all distinguished by a 
connecting member which connects a dye residue to a carrier group 
containing a ballast group and which is redox dependent in the strength of 
its linkage. 
A comprehensive survey of this subject may be found in Angew. Chem. Int. 
Ed. Engl. 22 (1983), 191-209, in which the most important of the known 
systems are described. 
Particularly advantageous redox active dye releasing compounds are those 
which may be represented by the formula 
EQU BALLAST--REDOX--DYE 
wherein 
BALLAST denotes a ballast group, 
REDOX denotes a redox.active group, i.e. a group which is oxidizable or 
reducible under the conditions of alkaline development and which is 
subject to varying degrees, depending on whether it is in the oxidized or 
reduced state, to an elimination reaction, a nucleophilic displacement 
reaction, hydrolysis or some other splitting reaction by which the DYE 
residue is split off, and 
DYE denotes the residue of a diffusible dye, e.g. a yellow, magenta or cyan 
dye, or the residue of a dye precursor.

Ballast groups enable the dye releasing compounds according to the 
invention to be incorporated in a diffusion-fast form in the hydrophilic 
colloids conventionally fast form in the hydrophilic colloids 
conventionally used in photographic materials. These groups are preferably 
organic groups, generally straight chained or branched aliphatic groups 
generally containing 8 to 20 carbon atoms and optionally also containing 
carbocyclic or heterocyclic and in some cases aromatic groups. These 
groups are connected to the remainder of the molecule either directly or 
indirectly, e.g. by way of one of the following groups: NHCO, NHSO.sub.2, 
NR wherein R denotes hydrogen or alkyl, O or S. The ballast group may in 
addition contain water-solubilizing groups such as sulpho groups or 
carboxyl groups, and these may be present in an anionic form. Since the 
diffusion properties depend on the molecular size of the whole compound, 
it is in some cases sufficient to use relatively short-chained groups as 
ballast groups, e.g. if the molecule as a whole is large enough. 
Redox-active carrier groups having the structure of BALLAST-REDOX-and 
corresponding dye releasing compound are known in a variety of forms. A 
detailed description need not be given here in view of the survey given in 
Angew. Chem. Int. Ed. Engl. 22 (1983) 191-209. 
Some examples of redox-active carrier groups from which a dye residue is 
split off as a result of imagewise oxidation or reduction are given below 
purely for illustration: 
##STR5## 
The groups in brackets are functional groups of the dye residue and are 
separated together with this residue from the remaining part of the 
carrier group. The functional group may be a substituent which has a 
direct influence on the absorption properties and possibly also 
complexforming properties of the released dye. On the other hand, the 
functional group may be separated from the chromophore of the dye by an 
intermediate or connecting member. Lastly, the functional group may be of 
some importance, in some cases together with the intermediate member, for 
the diffusion and mordanting properties of the released dye. Alkylene and 
arylene groups, for example, are suitable intermediate members. 
The dye residues may in principle be taken from any classes of dyes, 
provided they are sufficiently diffusible to be capable of diffusing from 
the light-sensitive layer of the light-sensitive material into an image 
receptor layer. The dye residues may be equipped with one or more alkali 
solubilizing groups for this purpose. Groups suitable for rendering these 
residues soluble in alkali include, for example, carboxyl groups, sulpho 
groups, sulphonamide groups and aromatic hydroxyl groups. Such alkali 
solubilizing groups may be preformed in the dye releasing compounds or 
they may result from the release of the dye residue from the carrier group 
attached to ballast groups. The following are suitable dyes: Azo dyes, 
azomethine dyes, anthraquinone dyes, phthalocyanine dyes, indigoid dyes 
and triphenylmethane dyes, including dyes which are in the form of 
complexes or capable of forming complexes with metal ions. 
The residues of dye precursors are residues of compounds which are 
converted into dyes in the course of the photographic process, in 
particular under the conditions of heat development, either by oxidation 
or by coupling or by complex formation or by release of an auxochromic 
group in a chromophoric system, for example by saponification. Dye 
precursors within this meaning may be leuco dyes, couplers or dyes which 
are converted into other dyes in the course of processing. Where it is not 
important to make a distinction between dye residues and residues of dye 
precursors, the latter are also referred to as dye residues hereinafter. 
Suitable dye releasing compounds are described, for example, in the 
following: U.S. Pat. Nos. 3,227,550, 3,443,939, 3,443,940, DE-A No. 1 930 
215, DE-A No. 2 242 762, DE-A No. 2 402 900, DE-A No. 2 406 664, DE-A No. 
2 505 248, DE-A No. 2 543 902, DE-A No. 2 613 005, DE-A No. 2 645 656, 
DE-A No. 2 809 716, DE-A No. 2 823 159, BE-A No. 861 241, EP-A No. 0 004 
399, EP-A No. 0 004 400, DE.A No. 3 008 588, DE-A No. 3 014 669 and GB-A 
No. 8 012 242. 
In some embodiments of the heat development process according to the 
invention, the dye releasing compounds may be present in a form which is 
oxidizable or capable of coupling whereas in others they may be present in 
a reducible form. Depending on whether the dye is released from the 
oxidized or the reduced form of dye releasing compound, the copy obtained 
from the original will be a negative or a positive copy when conventional, 
negatively operating silver halide emulsions are used. It is therefore 
possible to produce either positive or negative images as desired by 
suitable choice of the dye releasing systems. 
Oxidizable dye releasing compounds suitable for the heat developable 
recording materials according to the invention are described, for example, 
in DE-A No. 2 242 762, DE-A No. 2 505 248, DE-A No. 2 613 005, DE-A No. 2 
645 656 and GB-A No. 8 012 242. 
If the dye releasing compound is oxidizable, it constitutes a reducing 
agent which is oxidized by the silver halide which has been exposed 
imagewise or by the substantially light insensitive silver salt under the 
catalytic influence of the imagewise exposed silver halide, either 
directly or indirectly by the action of electron transfer agents ETA. 
Oxidation results in an imagewise differentiation in the capacity to 
release the diffusible dye. If, on the other hand, the dye releasing 
compound is reducible, then it is advantageously used in combination with 
a reducing agent which is present in a limited quantity, i.e. a so-called 
electron donor compound or an electron donor precursor compound, which in 
that case is present in the same layer of binder as the dye releasing 
compound, the light-sensitive silver halide and optionally the 
substantially light-insensitive silver salt. The assistance of electron 
transfer agents may also be advantageous when reducible dye releasing 
compounds are used in combination with electron donor compounds. 
For producing positive colour images from positive originals when negative 
silver halide emulsions are used it is suitable, for example, to use a 
recording material according to the invention which contains reducible dye 
releasing compounds corresponding to the following formula: 
##STR6## 
wherein R.sup.1 denotes alkyl or aryl, 
R.sup.2 denotes alkyl, aryl or a group which together with R.sup.3 forms a 
condensed ring, 
R.sup.3 denotes hydrogen, alkyl, aryl, hydroxyl, a halogen such as chlorine 
or bromine, amino, alkylamino, dialkylamino including cyclic amino groups 
(such as piperidino, morpholino), acylamino, alkylthio, alkoxy, aroxy, 
sulpho or a group which together with R.sup.2 completes a condensed ring, 
R.sup.4 denotes alkyl and 
R.sup.5 denotes alkyl or, preferably, hydrogen, and at least one of the 
groups R.sup.1 to R.sup.4 contains a ballast group. 
Reducible dye releasing compounds of this kind and others which are also 
suitable for the purpose of the present invention are described, for 
example, in DE-A No. 2 809 716, EP-A No. 0 004 399, DE-A No. 3 008 588 and 
DE-A No. 3 014 669. 
The electron donor compound used in combination with a reducible dye 
releasing compound at the same time serves as a reducing agent for the 
silver halide, the substantially light-insensitive silver salt and the dye 
releasing compound. Owing to the fact that the substantially 
light-insensitive silver salt and the dye releasing compound compete with 
each other in the oxidation of the electron donor compound but the former 
is always superior to the latter in the presence of exposed silver halide, 
it is the silver halide present which determines, according to a previous 
imagewise exposure, the areas of image within which the dye releasing 
compound is converted into its reduced form by the electron donor 
compound. 
Under the conditions of development, in the present case when the imagewise 
exposed colour photographic recording material is heated, the electron 
donor compound which is present in a limited quantity is oxidized by the 
substantially light-insensitive silver salt and the light-sensitive silver 
halide under the catalytic action of the latent image nuclei which have 
been produced in the silver halide by exposure, this oxidation depending 
on the degree of exposure which has taken place, and the electron donor 
compound is then no longer available for a reaction with the dye releasing 
compound. This results in an imagewise distribution of unused electron 
donor compound. 
Substances which have been described as electron donor compounds include, 
for example, non-diffusible or only slightly diffusible derivatives of 
hydroquinone, of benzisoxazolone, of p-aminophenol and of ascorbic acid 
(e.g. ascorbyl palmitate) (DE-A No. 2 809 716). 
Other examples of electron donor compounds are known from DE-A No. 2 947 
425, DE-A No. 3 006 268, DE-A No. 3 130 842, DE-A No. 3 144 037, DE-A No. 
3 217 877, EP-A No. 0 124 915 and Research Disclosure 24 305 (July 1984). 
It has been found that the above-mentioned electron donor compounds also 
satisfy the requirements under the conditions of heat development and are 
therefore suitable electron donor compounds for the purpose of the present 
invention. 
Particularly suitable are those electron donor compounds which are formed 
in the layer from electron donor precursor compounds under the conditions 
of heat development, i.e. electron donor compounds which before 
development are present in the recording material only in a masked form in 
which they are virtually ineffective. The initially inactive electron 
donor compounds are converted into their active form under the conditions 
of heat development, for example by the hydrolytic removal of certain 
protective groups. In the present case, the term "electron donor compound" 
is to be understood to include also the aforesaid electron donor precursor 
compounds. 
The above-mentioned essential constituents of the recording material used 
in the process according to the invention, namely the light-sensitive 
silver halide, the substantially light-insensitive, reducible silver salt 
optionally present and the dye releasing compound, optionally in 
combination with an electron donor compound, are present side by side as a 
dispersion in a binder. The binders may be hydrophobic or hydrophilic but 
hydrophilic binders are preferred, especially gelatine although this may 
be partly or completely replaced by other, naturally occurring or 
synthetic binders. Polyurethanes, for example, have proved to be suitable 
binders, optionally in combination with gelatine, as described, for 
example, in German Patent Application No. P 35 30 156.2. 
For the production of monochrome colour images. one or more dye releasing 
compounds which release dyes of a particular colour are associated with 
the light-sensitive silver halide and optionally light-insensitive silver 
salt in the light-sensitive layer of binder. The colour finally obtained 
may result from a mixture of several dyes. It is thereby possible to 
produce black-and-white images by accurate adjustment of several dye 
releasing compounds of different colours. For the production of 
multicoloured images, the colour photographic recording material used in 
the process according to the invention contains several, i.e. generally 
three associations of dye releasing compounds with their respective silver 
halides which are sensitized to different regions of the spectrum. In 
these associations, the region of absorption of the dye released from the 
dye releasing compound preferably corresponds substantially to the region 
of spectral sensitivity of the associated silver halide. The various 
associations of dye releasing compounds with silver halide may be 
accommodated in different layers of binder of the colour photographic 
recording material, in which case separating layers of a water-permeable 
binder such as gelatine are preferably placed between these different 
layers of binder, mainly to separate the different associations from one 
another and thus prevent colour deviation. In such a case, the colour 
photographic recording material used in the process according to the 
invention may contain, for example, a light-sensitive layer of binder in 
which the silver halide is mainly sensitive to red due to spectral 
sensitization, another light-sensitive layer of binder in which the silver 
halide is predominantly sensitive to green as a result of spectral 
sensitization and a third light-sensitive layer of binder in which the 
silver halide is predominantly sensitive to blue either due to its 
intrinsic sensitivity or as a result of spectral sensitization. The 
electron donor compounds optionally present in the three light-sensitive 
layers may be identical or different. 
Each of the above-mentioned associations of light-sensitive silver halide, 
substantially light-insensitive silver salt (if present) and dye releasing 
compound may also be used in the form of a so called complex coacervate. 
A complex coacervate is a form of dispersion in which a mixture of the 
required constituents is enclosed in a common shell of hardened binder. 
Dispersions of this kind are also known as packet emulsions. They are 
obtained by complex coacervation. 
By "complex coacervation" is meant the occurrence of two phases when an 
aqueous solution of a polycationic colloid is mixed with one of a 
polyanionic colloid to form a concentrated colloid phase (hereinafter 
referred to as complex coacervate) and a dilute colloid phase (hereinafter 
referred to as equilibrium solution) due to an electric interaction. The 
complex coacervate is separated from the equilibrium solution in the form 
of droplets and appears as a white cloudiness. It is generally assumed 
that when complex coacervation is carried out in the presence of a solid 
such as a silver halide or fine oil droplets, the complex coacervate 
encloses the solid or the droplets in the interior of colloid particles. 
As a result, a dispersion of coacervate particles is obtained in which the 
solid substance (in the present case the light-sensitive silver halide 
and, if present, the substantially light-insensitive silver salt) and oily 
droplets of a solution of the organic constituents (in the present case 
the dye releasing compounds and optionally other auxiliary substances) are 
enc-osed. The process is followed by hardening with a hardener so that the 
original form of the particles is not destroyed in the subsequent stages 
carried out for producing the photographic recording material, such as 
preparation of the casting solution and coating. The dispersion is 
advantageously cooled prior to hardening to a temperature of 25.degree. C. 
or lower, preferably 10.degree. C. or a lower, as a packet emulsion of 
good quality is thereby obtained. 
Methods for the preparation of a packet emulsion in which a colour 
producing substance is incorporated by complex coacervation are described, 
for example, in U.S. Pat. Nos. 3,276,869 and 3,396,026. 
The use of packet emulsions enables several emulsion components differing 
in their spectral sensitivity and the corresponding dye releasing 
compounds to be accommodated in a single layer of binder without the 
spectral association being lost and hence without any resulting colour 
deviation. This can be achieved because the amount of exposure of a 
particular silver halide particle almost exclusively determines the amount 
of dye released from that dye releasing compound which is present in the 
same coacervate particle (packet) as the silver halide. The use of packet 
emulsions thus enables a blue-sensitive, a green-sensitive and a 
red-sensitive silver halide emulsion, optionally together with additional, 
substantially light-insensitive, silver salt and spectrally associated dye 
releasing compounds to be accommodated in the same layer of binder without 
any risk of serious colour deviation. 
In addition to the components already mentioned, the colour photographic 
recording material used in the process of the invention may contain other 
constituents and auxiliary agents which may be required, for example, for 
carrying out the heat treatment and the concomitant transfer of colour. 
These additional constituents or auxiliary substances may be contained in 
a light-sensitive layer or in a light-insensitive layer. 
These auxiliary substances may include, for example, auxiliary developers, 
which generally have a developing action on exposed silver halide. In the 
present case, they mainly promote the reaction between the exposed silver 
salt (=silver salt in the presence of exposed silver halide) and the 
reducing agent, which is identical to the dye releasing compound when the 
latter is oxidizable but reacts with the dye releasing compound when the 
latter is reducible. Since these reactions mainly consist of a transfer of 
electrons, the auxiliary developers are also referred to as electron 
transfer agents ETA. Examples of suitable auxiliary developers include 
hydroquinone, pyrocatechol, pyrogallol, hydroxylamine, ascorbic acid, 
1-phenyl-3-pyrazolinone and derivatives thereof. Since the auxiliary 
developers also exert a catalytic function, they need not be present in 
stoichiometric quantities. The presence of up to half mol of auxiliary 
developer per mol of dye releasing compound in the layer is generally 
sufficient. The auxiliary developer may be incorporated in the layer, for 
example, from solutions in water-soluble solvents or in the form of 
aqueous dispersions which have been obtained with the aid of oil formers. 
Other auxiliary substances include, for example, basic compounds or 
compounds capable of releasing basic compounds when heat treated. Examples 
include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium 
carbonate, sodium acetate and organic bases, in particular amines such as 
trialkylamines, hydroxyalkylamines, piperidine, morpholine, 
dialkylaniline, p-toluidine, 2-picoline, guanidine and salts thereof, in 
particular salts with aliphatic carboxylic acids. Due to these basic 
compounds becoming available, the heat treatment produces a suitable 
medium in the light-sensitive layer and the adjacent layers for releasing 
the diffusible dyes from the dye releasing compounds and enabling them to 
be transferred to the image receptor sheet. 
The auxiliary substances may also include, for example, compounds which are 
capable of releasing water under the action of heat. These include in 
particular inorganic salts containing water of crystallisation, e.g. 
Na.sub.2 SO.sub.4.10H.sub.2 O, NH.sub.4 Fe(SO.sub.4).sub.2.12H.sub.2 O and 
compounds of the type of sodium benzotriazolate which crystallise as 
complexes with varying quantities of water (up to 24 mol H.sub.2 O); these 
have been described in U.S. Pat. No. 4,418,139. 
The water released on heating promotes the development and diffusion 
processes required for production of the image. 
The TEDMs described earlier in the text are also important auxiliary 
substances for the purpose of the present invention. These compounds, 
however, need not necessarily be present in the same layer as the 
light-sensitive silver halide and the dye releasing compounds. It is 
sufficient if any layer of binder which is in contact with the 
light-sensitive layers during the heat treatment contains the required 
quantity of the aforesaid TEDMs. On heating, the TEDM forms a suitable 
solubilizing medium assisting the development and dye diffusion processes, 
at least in those layers which take part in the development and dye 
diffusion processes. The TEDM according to the invention may thus be 
present in a light-sensitive layer containing silver halide and a colour 
producing compound or in a light-insensitive layer of binder or in several 
of the aforesaid layers but it may also be contained in an image receptor 
layer which is situated on the same layer support as the light-sensitive 
layers and together with these layers form a component of an integral 
recording material. Furthermore, the TEDM may be present in an image 
receptor layer of a separate image receptor material, provided only that 
contact is established with the light-sensitive layers of the heat 
developable photographic recording material during the heat treatment. 
Lastly, the TEDM according to the invention may be present in a dispersed 
form in an auxiliary sheet which is brought into contact with the 
light-sensitive recording material and together with this material is 
subjected to a heat treatment. A process of this kind is described, for 
example, in German Patent Application P 35 23 361.3. 
Without departing from the scope of the invention, the TEDM according to 
the invention may be used in combination with one or more of the so-called 
thermal solvents known in the art such as those described, for example, in 
DE-A No. 3 339 810, EP-A No. 0 119 615 and EP-A No. 0 122 512. 
Development of the imagewise exposed colour photographic recording material 
according to the invention covers the partial steps of silver halide 
development, production of an imagewise distribution of diffusible dyes 
and transfer of this imagewise distribution into the image receptor layer 
by diffusion. This development is initiated by subjecting the exposed 
recording material to a heat treatment in which the light-sensitive layer 
of binder is raised to a temperature e.g. in the region of 80.degree. to 
250.degree. C. for a period of about 0.5 to 300 seconds. Suitable 
conditions for the development processes, including dye diffusion, are 
thereby provided in the recording material without the use of a liquid 
medium, e.g. in the form of a developer bath. Diffusible dyes are released 
imagewise from the dye releasing compound in the course of development and 
transferred to an image receptor layer which is either an integral 
constituent of the colour photographic recording material according to the 
invention or is in contact with this material at least during the time of 
development. Imagewise development of silver, release of dye and transfer 
of colour thus take place synchronously in a one-step development process. 
Production of the colour image may also take place by a two-step 
development process with the colour photographic recording material 
according to the invention, in which case silver halide development and 
dye release take place in a first step and transfer of the colour image 
from the light-sensitive part to an image receptor part in contact 
therewith in a second step, e.g. by heating to a temperature of from 
50.degree. to 150.degree. C., preferably from 70.degree. to 90.degree. C., 
in which case diffusion auxiliaries (solvents) may be applied externally 
before lamination of the light-sensitive part with the image receptor 
part. 
The image receptor layer may thus be arranged on the same layer support as 
the light-sensitive element (single sheet material) or on a separate layer 
support (two-sheet material). It consists mainly of a binder containing 
mordant for fixing the diffusible dyes which are released from the 
non-diffusible dye releasing compounds. The mordants used for anionic dyes 
are preferably long chained quaternary ammonium or phosphonium compounds, 
e.g. those described in U.S. Pat. Nos. 3,271,147 and 3,271,148. 
Certain metal salts and their hydroxides which form difficultly soluble 
compounds with the acid dyes may also be used. Polymeric mordants should 
also be mentioned in this connection, such as those described in DE-A No. 
2 315 304, DE-A No. 2 631 521 or DE-A No. 2 941 818. The dye mordants are 
dispersed in the mordant layer in one of the usual hydrophilic binders, 
e.g. in gelatine, polyvinyl pyrrolidone or partially or completely 
hydrolysed cellulose esters. Some binders may, of course, also function as 
mordants, e.g. polymers of nitrogen-containing, optionally quaternary 
bases, such as N-methyl-4-vinylpyridine, 4-vinylpyridine or 
1-vinylimidazole, as described, for example, in U.S. Pat. No. 2,484,430. 
Other suitable mordanting binders are, for example, the guanylhydrazone 
derivatives of alkyl vinyl ketone polymers as described, for example, in 
U.S. Pat. No. 2,882,156, and guanylhydrazone derivatives of acyl styrene 
polymers as described, for example, in DE-A No. 2 009 498. The last 
mentioned binder, however, would generally be used in combination with 
other binders, e.g. gelatine. 
If the image receptor layer is to be left in layer contact with the 
light-sensitive element after development has been completed, an 
alkali-permeable, light-reflective layer of binder containing pigment is 
generally provided between the image receptor layer and the 
light-sensitive element to provide an optical separation between the 
negative and the positive and serve as aesthetically pleasing background 
for the transferred positive colour image. If the image receptor layer is 
arranged between the layer support and the light-sensitive element and 
separated from the latter by a preformed light-reflective layer, then the 
layer support must either be transparent so that the colour transfer image 
produced can be viewed through this layer or the light-sensitive element 
and the light-reflective layer must together be removed from the image 
receptor layer to expose the latter. On the other hand, the image receptor 
layer may be arranged as the uppermost layer of an integral colour 
photographic recording material, in which case the material is preferably 
exposed through the transparent layer support. 
EXAMPLE 1 
Preparation of the silver salt emulsions 
Emulsion 1 
34.0 g AgNO.sub.3 dissolved in 400 ml of water heated to 45.degree. C. were 
added in the course of 2 minutes, with stirring, to a solution heated to 
45.degree. C. of 4.0 g of gelatine in 2000 ml of water containing 26.0 g 
of benzotriazole (BTA). The reaction mixture was then stirred for a 
further 5 minutes and adjusted to pH 5.0 with a 5% Na.sub.2 CO.sub.3 
solution. The solution was flocculated by the addition of 40 ml of a 10% 
polystyrene sulphonic acid solution, cooling to 25.degree. C. and addition 
of 10% sulphuric acid (to pH 3.0-3.5) and then washed three times with 
1000 ml portions of water. The flocculate was heated to 45.degree. C. and 
adjusted to pH 6.0 with a 5% Na.sub.2 CO.sub.3 solution, 10 ml of a 1% 
aqueous phenol solution was added and the weight made up to 870 g with 
water. 
Emulsion 2 
102.0 g of AgNO.sub.3 dissolved in 600 ml of water were added in the course 
of 10 minutes to a solution heated to 50.degree. C. of 120.0 g of 
gelatine, 271.1 g of KBr and 4.98 g of KI in 6000 ml of H.sub.2 O. The 
reaction mixture was then stirred for 20 minutes at 50.degree. C. and 
cooled to 35.degree. C. 120 ml of a 10% polystyrene sulphonic acid 
solution were added dropwise and the reaction mixture was then cooled to 
20.degree. C. The mixture was then flocculated by the addition of 10% 
sulphuric acid (to pH 3.0-3.5) and washed three times with 700 ml portions 
of water. The emulsion was heated to 40.degree. C. and adjusted to pH 6.0 
with a 10% sodium hydroxide solution. Final weight 3510 g. 
For spectral sensitization (green sensitization), parts of Emulsion 2 
(crude emulsion) were melted at 40.degree. C., 4.times.10.sup.-4 mol of 
green-sensitizer (in methanolic solution or slurry) were added per mol of 
Ag, and the mixture was left to digest in a closed vessel for about 70 
minutes. The following spectral sensitizer was used. 
Green sensitizer 
##STR7## 
EXAMPLE 2 
Preparation of the dispersions 
Dispersion 1 (Dye releasing compound M-1) 
50.0 g of dye releasing compound M-1 were dissolved in 25 g of 
diethyllaurylamide and 150 ml of ethyl acetate and finely dispersed in 330 
g of a 10% aqueous gelatine solution in the presence of 2.6 g of sodium 
dodecylbenzene sulphonate. The auxiliary solvent was then removed with 
depressurized steam in a low pressure apparatus. 
Yield: 834 g of Dispersion 1. 
Dispersin 2 (Auxiliary developer precursor compound) 
62 g of auxiliary developer precursor compound were dissolved in 120 g of 
diethyllaurylamide and 150 ml of ethyl acetate and dispersed in 612 g of a 
10% aqueous gelatine solution in the presence of 3.5 g of sodium 
dodecylbenzene sulphonate. The auxiliary solvent was then removed as in 
the case of Dispersion 1. 
Yield: 997 g of Dispersion 2. 
The following compounds were used: 
Dye releasing compound M-1 
##STR8## 
Auxiliary developer precursor compound 
##STR9## 
EXAMPLE 3 
Image receptor part A 
The image receptor part of a photographic recording material for the dye 
diffusion transfer process was prepared by applying the following layers 
in succession to a baryta paper used as layer support. The quantities 
given are based in each case on 1 m.sup.2. 
1. A mordant layer containing 2 g of polyurethane mordant of 
4,4'-diphenylmethane diisocyanate and N-ethyl-diethanolamine quaternized 
with epichlorohydrin according to DE-A No. 2 631 521, Example 1, and 2 g 
of gelatine. 
2. A layer of 0.6 g of gelatine and 0.6 g of sodium alginate to which a 
hardener has been added. 
EXAMPLE 4 
The light-sensitive parts of colour photographic recording materials not 
according to the invention (comparison) and according to the invention for 
the dye diffusion transfer process were prepared as follows: 
Sample 1 (according to the invention) 
91.2 g of Emulsion 1 are melted at 40.degree. C. and 8.0 ml of a 4% aqueous 
solution of Triton.RTM. 100.times. are added. 
##STR10## 
34.4 g of Dispersion 1 (dye releasing compound M-1). 13.4 g of Dispersion 2 
(auxiliary developer precursor compound), 32.2 g of 20% gelatine and 64.0 
g of Emulsion 2, green-sensitized, were added successively and melted one 
after the other. 6.4 g of guanidine trichloroacetate dissolved in 60 ml of 
water and 3.2 g of Compound 15 dissolved in 7.2 g of water were finally 
added. The solution was applied to a layer support of polyethylene 
terephthalate to form a layer with a wet thickness of 50 .mu.m and coated 
with a 1% aqueous gelatine solution containing a hardener (wet layer 
thickness 60 .mu.m) and dried. 
Sample 2 (according to the invention) 
Method of preparation as for Sample 1 but using 3.2 g of Compound 1. 
Sample 3 Comparison (not according to the invention) 
Preparation as for Sample 1 but Compound 1 replaced by 3.2 g of water. 
Sample 4 Comparison (not according to the invention) 
Preparation as for Sample 1 but Compound 1 replaced by 3.2 g of Comparison 
Compound V 
##STR11## 
EXAMPLE 5 
The samples prepared according to Example 4 were exposed to 1000 Lux of a 
tungsten lamp for 5 seconds through a transparent yellow filter having a 
density of 1.25. The samples were then heated dry to 110.degree. C. for 
development (the development time is entered in the following Table). The 
samples were then left to swell in water for 10 seconds and laminated to 
the image receptor sheet (from Example 3) which had been left to swell in 
water for 30 to 60 seconds, and the laminated sheets were heated to 
75.degree. C. on a controlled heating bench for 2 minutes and then 
separated and immediately dried. Sharp, brilliant colour transfers were 
obtained on the image receptor sheets. The D.sub.min and D.sub.max values 
are shown in Table 1. 
TABLE 1 
______________________________________ 
Development Colour density 
time D.sub.min 
D.sub.max 
______________________________________ 
Sample 1 30 0.20 1.27 
Sample 1 40 0.21 1.45 
Sample 1 50 0.23 1.67 
Sample 1 60 0.25 1.85 
Sample 2 50 0.22 1.64 
Sample 3 50 0.10 0.27 
Sample 3 60 0.11 0.30 
Sample 3 240 0.41 1.51 
Sample 3 480 1.59 1.73 
Sample 4 50 0.19 0.89 
Sample 4 50 0.23 1.23 
______________________________________ 
Table 1 shows very clearly the powerful action of the compounds according 
to the invention as development accelerating substances. 
A comparison of Samples 1 and 2 with Sample 4 shows a marked improvement in 
the D.sub.min /D.sub.max relation and hence a substantially higher 
photographic activity with regard to D.sub.max development (corresponding 
to a marked increase in the relative photographic sensitivity) without 
undue rise of the D.sub.min. 
The compounds of the dipolar aprotic type used according to the invention 
are thus markedly superior to the thermal solvents of the state of the art 
due to their improved photographic properties.