U.S. patent number 3,650,749 [Application Number 04/827,145] was granted by the patent office on 1972-03-21 for photographic development.
This patent grant is currently assigned to Gevaert-AGFA N.V.. Invention is credited to Antoon Leon Vandenberghe, Jozef Frans Willems.
United States Patent |
3,650,749 |
Willems , et al. |
March 21, 1972 |
PHOTOGRAPHIC DEVELOPMENT
Abstract
Photographic silver halide elements are described which comprise
incorporated in a silver halide emulsion layer or another
water-permeable colloid layer a hydroquinone silver halide
developing agent precursor of which at least one of the hydroxyl
groups of said hydroquinone has been esterified to form a
hydrolyzable aliphatic acyloxy radical comprising a quaternary
ammonium group. Upon treatment of the exposed elements with an
alkaline solution the developing agent precursor hydrolyzes readily
to yield the active developing agent so that no delay in
development occurs. The resulting developed images are free from
spots, do not show fog and possess the desired sensitivity and
gradation with normal or even shorter length of development
time.
Inventors: |
Willems; Jozef Frans (Wilrijk,
BE), Vandenberghe; Antoon Leon (Hove, BE) |
Assignee: |
Gevaert-AGFA N.V. (Mortsel,
BE)
|
Family
ID: |
10260996 |
Appl.
No.: |
04/827,145 |
Filed: |
May 23, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Jun 10, 1968 [EN] |
|
|
27,524/68 |
|
Current U.S.
Class: |
430/234; 430/249;
430/435; 430/436; 430/485; 430/564; 430/955 |
Current CPC
Class: |
G03C
5/3021 (20130101); C07D 213/20 (20130101); G03C
1/42 (20130101); Y10S 430/156 (20130101) |
Current International
Class: |
C07D
213/20 (20060101); C07D 213/00 (20060101); G03C
1/42 (20060101); G03C 5/30 (20060101); G03c
005/30 () |
Field of
Search: |
;96/29,66 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Torchin; Norman G.
Assistant Examiner: Goodrow; John L.
Claims
We claim:
1. A photographic element comprising a support and at least one
silver halide emulsion layer, wherein said element comprises in the
said emulsion layer and/or in a colloid layer in water-permeable
relationship with the said emulsion layer a hydroquinone silver
halide developing agent precursor of which at least one of the
hydroxyl groups of said hydroquinone has been esterified to form a
hydrolyzable aliphatic acyloxy radical comprising a quaternary
ammonium group.
2. A photographic element according to claim 1, wherein said
hydroquinone silver halide developing agent precursor corresponds
to the general formula :
wherein :
Y stands for hydrogen or one or more substituents selected from
alkyl and halogen,
X stands for methylene or ethylene including methylene or ethylene
substituted by alkyl or aryl,
Q stands for an ammonium group of one of the formulas :
##SPC4##
wherein :
M stands for chlorine or bromine,
each of R.sub.1 and R.sub.2 stands for an alkyl group or an aralkyl
group or together represent the atoms necessary for completing a
heterocyclic ring,
R.sub.3 stands for an alkyl group or an aralkyl group,
R.sub.4 stands for an alkylene group, and
Z represents the atoms necessary to close a heterocyclic
nucleus,
A stands for hydrogen or the group
3. A photographic element according to claim 1, which comprises in
addition to the said developing agent precursor an auxiliary
photographic developing agent.
4. A photographic element according to claim 3, wherein said
auxiliary developing agent is a 1-aryl-3-pyrazolidinone developing
agent.
5. A photographic element according to claim 4, wherein said
1-aryl-3-pyrazolidinone developing agent is
1-phenyl-3-pyrazolidinone.
6. Image-receiving material for use in a silver complex diffusion
transfer process comprising an image-receiving layer and containing
in a water-permeable layer a hydroquinone developing agent
precursor of which at least one of the hydroxyl groups of said
hydroquinone has been esterified to form a hydrolyzable aliphatic
acyloxy radical comprising a quaternary ammonium group.
7. A process for forming a visible photographic image comprising
treating an exposed photographic element as claimed in claim 1 with
an alkaline solution.
8. A process for forming a visible photographic image comprising
treating an exposed photographic element according to claim 1, with
an alkaline solution comprising an 1-aryl-3-pyrazolidinone
developing agent.
9. A process according to claim 7, wherein said alkaline solution
is an alkaline solution comprising at least one compound selected
from sodium hydroxide, potassium hydroxide, sodium carbonate,
potassium carbonate, and borax.
10. A process for forming a visible photographic image according to
the silver complex diffusion transfer process according to which a
positive image of an original is obtained by development of an
image-wise exposed light-sensitive silver halide material and
diffusion of the non-developed complexed silver halide from the
emulsion layer of said material to an image-receiving material
where the complexed silver halide is converted into a silver
containing image in the presence of development nuclei or
substances capable of forming such nuclei characterized in that
said light-sensitive silver halide material and/or the said
image-receiving material comprises a hydroquinone developing agent
precursor of which at least one of the hydroxyl groups of said
hydroquinone has been esterified to form a hydrolyzable aliphatic
acyloxy radical comprising a quaternary ammonium group and in that
development is effected by means of an alkaline solution.
11. A process according to claim 10, wherein said process is
carried out in the presence of an 1-aryl-3-pyrazolidinone
developing agent.
12. A process according to claim 10, wherein said alkaline solution
is an alkaline solution comprising at least one compound selected
from sodium hydroxide, potassium hydroxide, sodium carbonate,
potassium carbonate, and borax.
Description
The present invention relates to photographic materials and to a
method of developing said materials. More particularly the present
invention relates to photographic materials having incorporated
therein photographic developing agents and to a method of
processing and using the same.
An exposed photographic element comprising a support having at
least one silver halide emulsion layer thereon is commonly
developed by means of a developing solution comprising a silver
halide developing agent. This developing solution after having been
used for some time becomes less efficient among other reasons by
aerial oxidation so that it should be frequently replenished or
replaced, particularly when no or little preservative such as
sodium sulphite is present in the said developing solution.
In order to overcome these inconveniences it is known to
incorporate developing agents into the photographic material itself
and to initiate development of the exposed material by treatment
with alkaline solutions. However, due to the presence of reducing
functions said developing agents have an adverse influence upon the
silver halide emulsion, particularly high-sensitive emulsions.
Therefore it has been proposed to incorporate the developing agent
under a chemically masked form into the photographic material. For
instance, it has been proposed to incorporate an organic or a
substantially water-insoluble inorganic ester of a polyhydroxy
benzene compound in at least one colloid layer of the photographic
material. Although these so-called developer precursor compounds
have a high stability in the emulsion layer and the absence of
reducing functions in their molecule whereby any marked adverse
influence upon the light-sensitive silver halide emulsion is
excluded, they show the disadvantage of being hydrolyzed very
slowly in the alkaline activating bath so that a delay in release
of active developer and thus in development is involved.
In United States Pat. No. 3,246,988 of Ralph F. Porter, Thomas E.
Gompf, issued Apr. 19, 1966 it has been proposed to use as
developer precursor compound for incorporation into a photographic
light-sensitive material halogenated esters of 1,4-dihydroxy
benzene compounds. These halogenated esters of 1,4-dihydroxy
benzene compounds show the advantage over unsubstituted esters of
the said compounds of being more rapidly hydrolyzed in the alkaline
activating bath.
It has now been found that hydroquinone compounds wherein at least
one of the hydroxyl groups has been esterified to form a
hydrolyzable aliphatic acyloxy group comprising a quaternary
ammonium substituent are very effective developing agent precursors
for use in light-sensitive silver halide material, which hydrolyze
in an alkaline activator bath to release the active developer even
more rapidly than the corresponding haloacyloxy compounds.
The invention in its broadest aspect consists of the said
hydroquinone compound. Also in accordance with the invention a
photographic element is provided comprising a support and at least
one light-sensitive silver halide emulsion layer and integral with
said photographic element, e.g., in a light-sensitive emulsion
layer and/or in a colloid layer in water-permeable relationship
therewith a hydroquinone developing agent precursor wherein at
least one of the hydroxyl groups of said hydroquinone compound has
been esterified to form a hydrolyzable aliphatic acyloxy radical
comprising a quaternary ammonium group. The benzene ring of the
hydroquinone compounds can contain any of the conventional
substituents such as alkyl (e.g., methyl, ethyl, t-butyl, N-hexyl,
n-octyl, etc.) and halogen e.g., chlorine, bromine, etc.).
The novel hydroquinone silver halide developing agent precursors of
use according to the present invention can be represented more
particularly by the following general formula :
wherein :
Y stands for hydrogen or one or more substituents selected from
alkyl such as methyl, ethyl, t-butyl, etc. and halogen such as
chlorine, bromine,
X stands for methylene or ethylene including methylene or ethylene
substituted by alkyl or aryl,
Q stands for an ammonium group of one of the formulas :
##SPC1##
wherein :
M stands for chlorine or bromine,
each of R.sub.1 and R.sub.2 stands for an alkyl group or an aralkyl
group or together represent the atoms necessary for completing a
heterocyclic ring, e.g., morpholine, pyrrolidine and
piperidine,
R.sub.3 stands for an alkyl group or an aralkyl group,
R.sub.4 stands for an alkylene group, and
Z represents the atoms necessary to close a heterocyclic nucleus
such as pyridine,
A stands for hydrogen or the group
By the term hydroquinone silver halide developing agent precursor
is to be understood a developing agent having no developing action
before the development is actually desired; when this developer
precursor compound is treated with aqueous baths, particularly with
an alkaline aqueous bath the ester group(s) is (are) split off by
hydrolysis and the original, actual hydroquinone developing agent
is set free.
The present invention also provides a process for developing a
photographic silver image in a silver halide emulsion layer by
incorporating in said emulsion layer and/or in a colloid layer in
water-permeable relationship with said emulsion layer, e.g., an
undercoat or overcoat for such emulsion layer, a developer
precursor compound as defined above and by carrying out the
development by means of an alkali solution.
In the presence of aqueous alkali, the developer precursor
compounds of the invention hydrolyze readily to yield the
corresponding active hydroquinone silver halide developing agents
so that no delay in development is involved. Indeed, the quaternary
ammonium group accelerates hydrolysis of the ester group. Moreover,
the images obtained are free from spots, do not show fog or defects
caused by desensitization and possess the desired sensitivity and
gradation with normal length or even shorter length of development
time.
The developer precursor compounds of the invention are better
water-soluble than unsubstituted esters or halogenated esters of
1,4-dihydroxy benzenes and thus need not be incorporated in the
photographic material in dispersed form. By the presence of the
quaternary nitrogen atom the compounds of the invention can be
absorbed to the silver halide grains thus creating very favorable
circumstances for rapid development. It would appear that they have
the same favorable development action as in the case when using
hydroquinone and quaternary ammonium compounds separately.
Representative developing agent precursor compounds according to
the present invention and corresponding to the above general
formula are : ##SPC2##
As is illustrated by some preparations hereinafter, the development
precursor compounds according to the present invention can be
prepared by reaction of the corresponding haloacyl monoesters or
diesters with compounds of the following formulas 1 to 4 :
##SPC3##
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and Z have the same
significance as given above. When the haloacyl esters are allowed
to react with compounds of formulas (1) and (3) the said compounds
are used in amounts exceeding those of the haloacyl esters whereas
in the case they are allowed to react with compounds of formulas
(2) and (4) the haloacyl esters are used in amounts exceeding those
of the said compounds.
The haloacyl monoesters and diesters of use in the preparation of
the developing agent precursor compounds of the invention can be
prepared as described in U.S. Pat. No. 3,246,988 of Ralph F. Porter
and Thomas E. Gompf, issued Apr. 19, 1966.
PREPARATION 1 : COMPOUND 1
To a solution of 37.3 g. (0.2 mole) of the chloroacetyl monoester
of hydroquinone in 200 ml. of acetone 40 ml. (0.28 mole) of
triethylamine are added. The mixture is refluxed for 6 hours and
the precipitate formed is filtered by suction and washed with
water.
Yield : 37 g. (65 %). Melting point : 215.degree. C.
PREPARATION 2 : COMPOUND 7
To a solution of 37.3 g. (0.2 mole) of the chloroacetyl monoester
of hydroquinone in 200 ml. of acetone 28.3 g. (0.28 mole) of
N-methylmorpholine are added. The mixture is refluxed for 8 hours
and the precipitate formed is filtered by suction and washed with
acetone.
Yield : 37 g (64 %). Melting point : 220.degree. C.
PREPARATION 3 : COMPOUND 8
To a solution of 37.3 g. (0.2 mole) of the chloroacetyl monoester
of hydroquinone in 200 ml. of acetone 24 g. (0.3 mole) of pyridine
are added. The mixture is refluxed for 6 hours with stirring
whereupon the oily precipitate is separated. The product is
purified by pouring a methanolic solution thereof into ether.
Yield : 18 g. (34 %). Melting point : 210.degree. C.
PREPARATION 4 : COMPOUND 10
To a solution of 56 g. (0.3 mole) of the chloroacetyl monoester of
hydroquinone in 500 ml. of acetone a solution of 21.75 g. (0.125
mole) of 1,6-bis(dimethylamino) hexane in 50 ml. of acetone is
added dropwise with stirring. The mixture is refluxed for 2 hours
and the precipitate formed is filtered off and purified by boiling
in acetonitrile.
Yield : 52.5 g. (77 %). Melting point : 230.degree. C.
PREPARATION 5 : COMPOUND 12
To a solution of 52.6 g. (0.2 mole) of the chloroacetyl diester of
hydroquinone in 200 ml. of acetone 60.6 g. (0.6 mole) of
triethylamine are added. The mixture is stirred for 6 hours at room
temperature and then left standing overnight. The precipitate
formed is filtered by suction and purified by pouring an ethanolic
solution thereof into ether.
Yield : 47 g (50 %). Melting point : 260.degree. C.
The developer precursor compounds of use according to the present
invention can be incorporated in a photographic silver halide
emulsion suitable for preparing a light-sensitive silver halide
emulsion layer of a photographic element or into a colloidal
dispersion of a water-permeable hydrophilic colloid suitable for
preparing a colloid layer in water-permeable relationship with a
light-sensitive silver halide emulsion layer of a photographic
element, e.g., an undercoat or overcoat for such emulsion
layer.
The developer precursor compounds of the invention can be
incorporated into said silver halide emulsion or into said
colloidal dispersion by mixing a solution of the precursor compound
in a suitable solvent, preferably water, with the said silver
halide emulsion or the said colloidal dispersion prior to coating.
When incorporating the developer precursor into a silver halide
emulsion, the solution of said developer precursor may be added
during no matter what step of emulsion preparation and preferably
just before coating of the emulsion. The solution of the developing
agents may also first be homogeneously admixed with a hydrophilic
colloid composition, e.g., aqueous gelatin whereupon the whole is
mixed with the photographic emulsion.
The concentration of developer precursor according to the present
invention will vary markedly depending upon the particular chemical
compound involved, the particular process in which the photographic
element is to be used, and the location of the compound within the
photographic element. When incorporated in the silver halide
emulsion layer the amount of development precursor according to the
present invention per mole of silver halide is generally such that
upon treatment with the activator solution from 0.1 mole to 4
moles, preferably from 0.25 mole to 2 moles, of hydroquinone are
set free. When incorporated in another colloid layer which is in
contact with or which will come into contact with the silver halide
emulsion layer on development somewhat larger concentrations can be
used.
The photographic elements of the present invention comprising a
photographic development precursor compound either in a
photographic silver halide emulsion layer and/or in another colloid
layer in water-permeable relationship with the said emulsion layer
can be developed, after exposure, by means of a mere alkaline
activator bath. These alkaline activator baths for development of
the photographic element incorporating the developing agents
according to the present invention, can be of different
composition. Although a simple solution of an alkaline material,
e.g., an aqueous solution of sodium hydroxide, potassium hydroxide,
sodium carbonate, potassium carbonate, borax, etc., will suffice,
it may be advisable to add some other additives such as wetting
agents, preserving agents such as sodium sulphite, activators,
silver halide solvents, superadditive developing agents, etc.
The activator solutions may be applied to an exposed photographic
element according to the present invention in any known way such as
by dipping, spraying, etc.
The photographic element developed according to the present
invention can be stabilized by conventional fixation or by
stabilization. As a matter of fact the developing agent precursors
of the invention are particularly suitable for use in photographic
elements intended for stabilization processing, which elements
preferably comprise developing agents so that the developing bath
can be limited to a mere activator bath. For more details about
stabilization processing there can be referred to A. A. Newman "The
Chemistry of stabilization processing," The British Journal of
Photography Nov. 1967, p. 1,009 and the literature cited
therein.
The photographic silver halide emulsions of use according to the
present invention may be of any type, e.g., spectrally sensitized
and non-sensitized emulsions, X-ray emulsions and emulsions
sensitive to infra-red radiation. They may be high-sensitive
negative emulsions as well as rather low sensitive positive
emulsions. The emulsions may be orthochromatic or panchromatic.
Various silver salts may be used as light-sensitive salt, e.g.,
silver bromide, silver iodide, silver chloride or mixed silver
halides, e.g., silver chloro-bromide or silver bromoiodide.
The silver halides are dispersed in the common hydrophilic colloids
such as gelatin, casein, polyvinyl alcohol, carboxymethylcellulose,
sodium alginate, etc., gelatin being however favored.
The light-sensitive emulsions may be chemically as well as
optically sensitized. They may be chemically sensitized by
effecting the ripening in the presence of small amounts of sulphur
containing compounds such as allyl thiocyanate, allyl thiourea,
sodium thiosulphate, etc. The emulsions may also be sensitized by
means of reducing agents for instance tin compounds as described in
French Pat. No. 1,146,955 filed Apr. 11, 1956, by Gevaert
Photo-Producten N.V., Belgian Patent No. 568,687 filed June 18,
1958 by Gevaert Photo-Producten N.V. and in U.S. Pat. No. 2,487,850
of Burt H. Carroll issued Nov. 15, 1949, imino-amino methane
sulphinic acid compounds as described in British Patent No. 789,823
filed Apr. 29, 1955 by Gevaert Photo-Producten N.V. and small
amounts of noble metal compounds such as gold, platinum, palladium,
iridium, ruthenium and rhodium. They may be optically sensitized by
means of cyanine and merocyanine dyes.
It is evident that other additives such as development
accelerators, anti-fogging agents, stabilizers, sensitizers,
anti-oxidizing agents, may also be incorporated into the
composition of the silver halide emulsion layer or other
water-permeable colloid layer.
Examples of development accelerators which may be added to the
emulsion layer or other water-permeable colloid layer are the
polyoxyalkylene derivatives such as those described in U.S. Pat.
Nos. 2,531,832 of William Alexander Stanton, issued Nov. 28, 1950,
2,533,990 of Ralph Kingsley Blake issued Dec. 12, 1950, 3,210,191
of J. Willems, J. De Munck, and R. Thiers issued Oct. 5, 1965 and
3,158,484 of J. Willems, R. Thiers and J. De Munck issued Nov. 24,
1964 and in United Kingdom Pat. Nos. 920,637 filed May 7, 1959 by
Gevaert Photo-Producten N.V., and 991,608 filed June 14, 1961 by
Kodak Co., as well as the amino-N-oxides as described in United
Kingdom Pat. No. 1,121,696 filed Oct. 7, 1965 by Gevaert-Agfa
N.V.
Examples of stabilizers and antifoggants are heterocyclic nitrogen
containing thioxo compounds such as benzothiazoline-2-thione and
1-phenyl-2-tetrazoline-5-thione and particularly compounds of the
hydroxy-triazolopyrimidine type (azaindolizines). The emulsions may
further be stabilized with mercury compounds. Suitable mercury
compounds are for instance the mercury compounds described in
Belgian Pat. Nos. 524,121, filed Nov. 7, 1953 by Kodak Co., 677,337
filed Mar. 4, 1966 and 707,386 filed Dec. 1, 1967 both by
Gevaert-Agfa N.V., and in U.S. Pat. No. 3,179,520 of Yoshio Miura,
Akira Kiumai and Yosuke Nakajima issued Apr. 20, 1965.
The stabilizers, antifoggants and development accelerators may also
be present in the alkaline activator solution.
The developer precursor compounds according to the present
invention can also be used in combination with other auxiliary
developing agents present either in the photographic element like
the precursor compounds or in the activator solution. Typical
auxiliary developing agents include 1-phenyl-3-pyrazolidinone and
derivatives such as 1-p-tolyl-3-pyrazolidinone,
1-phenyl-5-methyl-3-pyrazolidinone,
1-phenyl-4,4-dimethyl-3-pyrazolidinone,
1-acetamidophenyl-3-pyrazolidinone, etc.
The developer precursors of the present invention can be used in
the light-sensitive material and/or in the image-receiving material
used in the application of the silver complex diffusion transfer
process, the principle of which is described in United Kingdom Pat.
Nos. 614,155 filed Nov. 2, 1939 and 654,630 filed Sept. 4, 1946
both by Gevaert Photo-Producten N.V. and in German Pat. No. 887,733
filed Jan. 24, 1941 by Agfa A.G.
For more details concerning the silver complex diffusion transfer
process, the different embodiments of the materials and apparatus
used therein, there can be referred to "Process in Photography"
1955-1958, pp.24-36 and the patent literature cited therein. In the
silver complex diffusion transfer process it may also be
advantageous to use in addition to the development precursors of
the invention auxiliary developers which may be present in the said
image-receiving material and/or light-sensitive material and/or the
treating bath.
The activator solutions which are used in accordance with the
present invention are stable for extended periods of time and not
subject to decomposition reactions so common to conventional
photographic developing solutions when storing these. No special
precautions are required to prevent oxidation of the activator
solutions since they are inherently quite stable.
The following examples will serve to illustrate the use of the
development precursors according to the present invention.
EXAMPLE 1
An ordinary gelatino silver chloride emulsion was prepared and
divided into ten aliquot portions. To these ten aliquot emulsion
portions were added separately at a concentration of 0.65 mole per
mole of silver chloride : hydroquinone, p-chloroacetoxyphenol,
1,4-bis(chloro-acetoxy)benzene, compounds 1, 3, 5, 7, and 8 and at
a concentration of 0.325 mole per mole of silver halide : compounds
10 and 11. The ten emulsions were then coated separately on
ordinary photographic film supports and dried.
The elements obtained were exposed and developed by immersing them
in a bath of the following composition :
potassium bromide 1 g. anhydrous sodium sulphite 30 g. anhydrous
sodium carbonate 30 g. water to make 1,000 ml.
The elements comprising p-chloroacetoxyphenol and
1,4-bis(chloroacetoxy)benzene showed no visible image after 60 sec.
of development and the element comprising hydroquinone only a very
faint image after 60 sec. of development. The elements comprising
compounds 1, 3, 7 and 8 showed a faint image already after 20 sec.
and a very good image after 60 sec. of development. The elements
comprising compounds 5 and 10 showed a faint image already after 5
sec. of development and an excellent image after 30 seconds of
development. Finally, the element comprising compound 11 showed a
very good image already after 5 sec. of development and an
excellent image after 20 sec. of development.
From this example it clearly appears that the development
precursors of the present invention have marked advantages over the
halogenated acyl esters of hydroquinone and over hydroquinone
itself.
From a comparison of the results obtained there cannot only be
concluded that the ammonium compounds hydrolyzed more rapidly in
the alkaline treating bath than the corresponding halogenated acyl
esters but moreover that the ammonium compounds act as developments
accelerators (compare the results obtained with hydroquinone itself
and those obtained with the compounds of the invention).
EXAMPLE 2
Two photographic elements A and B were prepared in an analogous way
as the photographic elements of Example 1, using as development
precursors:compound 12 and 1,4-bis (chloroacetoxy)benzene
respectively at a concentration of 0.65 mole per mole of silver
halide.
The two elements were exposed and developed by immersing them in a
bath of the following composition :
potassium bromide 1 g. borax 25 g. anhydrous sodium sulphite 25 g.
1-phenyl-3-pyrazolidinone 200 mg. water to make 1 liter
Element A showed an excellent image after a development time of 30
seconds whereas element B showed only a faint image even after 60
seconds of development which shows that the dihaloacyl esters of
hydroquinone are very slowly hydrolyzed as compared with
corresponding compounds according to the present invention.
EXAMPLE 3
A conventional gelatino silver chlorobromide emulsion for
stabilization processing (60 mole percent of silver bromide and 40
mole percent of silver chloride) comprising the common emulsion
addenda was divided into three aliquot portions A, B and C. To
these aliquot portions were added separately per mole of silver
halide : 0.65 mole of hydroquinone, 0.65 mole of compound 1 and
0.325 mole of compound 10 respectively. The emulsion portions were
then coated separately on conventional baryta-coated paper supports
and dried.
The elements obtained were exposed and developed by means of the
following activator solution :
anhydrous sodium sulphite 25 g. anhydrous sodium carbonate 40 g.
potassium bromide 1 g. water to make 1,000 ml.
After a development time of 5 min. element A showed no visible
image whereas element B showed an image with maximum density = 0.30
and element C an image with maximum density = 2.
When identical photographic elements A', B' and C' were developed,
after exposure by means of an activator solution comprising in
addition to the above ingredients 100 mg. of
1-phenyl-3-pyrazolidinone normal sensitometric results were
obtained with all elements A', B' and C'. However, when storing the
developed elements for 5 days at 57.degree. C. and 36 percent of
relative humidity the maximum density of the image of element A'
was markedly reduced whereas the images of elements B' and C'
remained practically unchanged.
* * * * *