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Description  |
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This invention relates in general to photography and in particular to the
black-and-white development of photographic elements. More specifically,
this invention relates to the development of high contrast photographic
elements, such as lithographic films used in the field of graphic arts.
High contrast development of lithographic films is ordinarily carried out
using special developers which are known in the art as "lith" developers.
In conventional "lith" developers, high contrast is achieved using the
"lith effect" (also referred to as infectious development) as described by
J. A. C. Yule in the Journal of the Franklin Institute, Vol. 239, 221-230,
(1945). This type of development is believed to proceed autocatalytically.
To achieve "lith effect" development, a low, but critical, concentration
of free sulfite ion is maintained by use of an aldehyde bisulfite adduct,
such as sodium formaldehyde bisulfite, which, in effect, acts as a sulfite
ion buffer. The low sulfite ion concentration is necessary to avoid
interference with the accumulation of developing agent oxidation products,
since such interference can result in prevention of infectious
development. The developer typically contains only a single type of
developing agent, namely, a developing agent of the dihydroxybenzene type,
such as hydroquinone.
Conventional "lith" developers suffer from serious deficiencies which
restrict their usefulness. For example, the developer exhibits low
capacity as a result of the fact that it contains hydroquinone as the sole
developing agent. Also, the aldehyde tends to react with the hydroquinone
to cause undesirable changes in development activity. Furthermore, the low
sulfite ion concentration is inadequate to provide effective protection
against aerial oxidation. As a result, a conventional "lith" developer is
lacking in stability and tends to give erratic results depending on the
length of time that it has been exposed to the air.
As an alternative to using a hydroquinone developer with a low sulfite
content to achieve high contrast development, it is possible to utilize a
hydrazine compound, either in the photographic element or in the developer
solution, which will promote high contrast. As described in Simson et al,
U.S. patent application Ser. No. 57,042, "High Contrast Photographic
Emulsions And Elements And Processes For Their Development," filed July
12, 1979, as a continuation of U.S. Pat. application Ser. No. 944,940
filed Sept. 22, 1978, use of a hydrazine compound permits the use of
auxiliary developing agents in combination with the dihydroxybenzene
developing agent in order to increase development capacity. It also
permits the use of relatively high sulfite concentrations to protect the
developing agents against oxidation and thereby increase developer
stability. However, high pH levels in developers containing hydrazine
compounds, or in developers used with photographic elements, such as those
of Simson et al, which contain hydrazine compounds, for example a pH of
12.0, are desirable in order to get the maximum improvement in contrast
from the use of the hydrazine compound. The use of such high pH levels
means that the effective life of the developing solution is relatively
short. It would, accordingly, be highly advantageous to provide a
developing solution that provides the advantage of a long effective
working life in addition to the advantages of high capacity and a high
degree of stability.
In accordance with this invention, it has been discovered that the above
advantage is achieved by the use of an aqueous alkaline developing
solution which contains a combination of developing agents that gives good
capacity, namely a combination of a dihydroxybenzene developing agent and
a 3-pyrazolidone developing agent; which contains a hydrazine compound, or
is utilized with a photographic element containing a hydrazine compound,
to obtain the beneficial effects which such compounds exert on contrast
characteristics; which contains a sulfite preservative at a level
sufficient to provide good stability characteristics; which contains an
amino compound in an amount which is sufficient to promote contrast; and
which utilizes a reduced pH level, that is a pH of below 12, to thereby
enhance the effective life of the solution. Quite unexpectedly, it has
been found that the amino compound permits the use of a reduced pH level,
while retaining the desired high contrast characteristics, and thereby
achieves the important objective of prolonging the effective life of the
developer, that is, of increasing the length of time that the developer
can be stored and/or used and still provide acceptable development
characteristics.
It is well known to use hydrazine compounds, either in photographic
developers or in a photographic element, to promote high contrast
development. Thus, for example, such use of hydrazine compounds is
described in Smith et al U.S. Pat. No. 2,410,690, Stauffer et al U.S. Pat.
No. 2,419,974, Trivelli et al U.S. Pat. No. 2,419,975 and Hunsberger U.S.
Pat. No. 2,892,715, and in an article by Stauffer, Smith and Trivelli
entitled, "The Influence Of Photographic Developers Containing Hydrazine
Upon The Characteristic Curves of Photographic Materials," Journal of the
Franklin Institute, Vol. 238, pages 291-298, October 1944. It is also well
known to use amino compounds in developers employed in high contrast
development. Such compounds have been used for a variety of purposes such
as the use for the purpose of increasing stability and reducing drag
streaks and dot distortions described in Masseth U.S. Pat. No. 3,573,914;
the use in combination with a carbonylbisulfite and a carbonate to achieve
stability and good dot quality described in Hayashi et al U.S. Pat. No.
4,022,621; the use as an agent which aids in dissolving dihydroxybenzene
developers and which promotes dot quality and avoids contraction of
half-tone gradation described in British Pat. No. 1,359,444 published July
10, 1974; and the use as a pH controlling agent described in Sincius et
al, U.S. Pat. No. 4,172,728. It is also known from Dickerson U.S. Pat. No.
2,882,152 to utilize a combination of hydrazine and triethanolamine in a
black-and-white developing composition as a development accelerator.
However, it is not known to the prior art to utilize both an amino
compound and a hydrazine compound to promote the formation of high
contrast at reduced pH levels, as described herein, and this novel
combination of features has been surprisingly found to provide a highly
desirable combination of advantageous characteristics in high contrast
processing, namely the combination of high capacity, a high degree of
stability, and a long effective life.
In the method of this invention, the amino compound must be used in a
contrast-promoting amount. Such use of an amino compound is distinct from
the use of certain amino compounds, such as ethylenediaminetetraacetic
acid, as chelating or sequestering agents, as is disclosed in the
aforesaid Simson et al patent application Ser. No. 57,042.
Ethylenediaminetetraacetic acid is used in small amounts, such as amounts
of about one gram per liter of developer solution, for the purpose of
functioning as a chelating or sequestering agent, but use of such small
amounts of ethylene-diaminetetraacetic acid has no significant
contrast-promoting effect. In the present invention, in which an amino
compound is employed to promote contrast, it will usually be desirable to
also include ethylene-diaminetetraacetic acid, or other similar chelating
or sequestering agent, in the developing solution, in order to sequester
calcium ions, and thereby prevent the formation of undesirable
precipitates.
Photographic elements which can be processed in the novel high contrast
developing solutions of this invention are not limited to "lith" films.
Typically, "lith" films contain high chloride emulsions (at least about 60
percent by weight silver chloride based on total silver halide), most
usually in the form of silver chlorobromides or silver chlorobromoiodides.
Such films give excellent results when used in the novel high contrast
developing solutions of this invention. However, the novel high contrast
developing solutions of this invention can also be usefully employed with
other types of silver halide photographic elements, for example with
elements utilizing silver bromide or silver bromoiodide emulsions. To
achieve the benefits of this invention, the hydrazine compound can be
incorporated in the photographic element or in the developing solution,
the essential requirement being that it be present during development of
the exposed element. Incorporation of a hydrazine compound in both the
photographic element and in the developing solutions is, of course, a
further alternative that can be utilized where it is desired to do so.
The contrast or "gamma" of a photographic element refers to the rate of
change of density with exposure and is measured by the slope of the
straight line portion of the characteristic curve. Photographic elements
processed in the novel developing solutions of this invention typically
exhibit very high contrast, by which is meant a gamma of greater than 10.
As used herein, the term "a hydrazine compound" is intended to include
hydrazine and hydrazine derivatives, including those which are suited for
incorporation in developing solutions and those which are suited for
incorporation in photographic elements.
Hydrazine (H.sub.2 N-NH.sub.2) is an effective contrast-promoting agent
which can be incorporated in the developing solutions of this invention.
As an alternative to the use of hydrazine, any of a wide variety of
water-soluble hydrazine derivatives can be added to the developing
solution. Preferred hydrazine derivatives for use in the developing
solutions of this invention include organic hydrazine compounds of the
formula:
##STR1##
where R.sup.1 is an organic radical and each of R.sup.2, R.sup.3 and
R.sup.4 is a hydrogen atom or an organic radical. Organic radicals
represented by R.sup.1, R.sup.2, R.sup.3 and R.sup.4 include hydrocarbyl
groups such as an alkyl group, an aryl group, an aralkyl group, an alkaryl
group, and an alicyclic group, as well as hydrocarbyl groups substituted
with substituents such as alkoxy groups, carboxy groups, sulfonamido
groups, and halogen atoms.
Particularly preferred hydrazine derivatives for incorporation in the
developing solutions of this invention include alkylsulfonamido aryl
hydrazines such as p-(methylsulfonamido) phenylhydrazine and
alkylsulfonamidoalkyl aryl hydrazines such as p-(methylsulfonamidomethyl)
phenylhydrazine.
In the practice of this invention, it is preferred that the hydrazine
compound be incorporated in the photographic element. For example, it can
be incorporated in a silver halide emulsion used in forming the
photographic element. Alternatively, the hydrazine compound can be present
in a hydrophilic colloid layer of the photographic element, preferably a
hydrophilic colloid layer which is coated to be contiguously adjacent to
the emulsion layer in which the effects of the hydrazine compound are
desired. It can, of course, be present in the photographic element
distributed between or among emulsion and hydrophilic colloid layers, such
as undercoating layers, interlayers, and overcoating layers.
Photographic elements which are particularly preferred for use in the
method of this invention include elements described in the aforesaid
Simson et al U.S. Pat. application Ser. No. 57,042, the disclosure of
which is incorporated herein by reference. These elements contain a
hydrazine compound of the formula:
##STR2##
wherein R.sup.1 is a phenyl nucleus having a Hammet sigma value-derived
electron withdrawing characteristic of less than +0.30.
As disclosed in Simson et al U.S. Pat. application Ser. No. 57,042, R.sup.1
can take the form of a phenyl nucleus which is either electron donating
(electropositive) or electron withdrawing (electronegative); however,
phenyl nuclei which are highly electron withdrawing produce inferior
nucleating agents. The electron withdrawing or electron donating
characteristic of a specific phenyl nucleus can be assessed by reference
to Hammett sigma values. The phenyl nucleus can be assigned a Hammett
sigma value-derived electron withdrawing characteristic which is the
algebraic sum of the Hammett sigma values of its substituents (i.e., those
of the substituents, if any, to the phenyl group). For example, the
Hammett sigma values of any substituents to the phenyl ring of the phenyl
nucleus can be determined algebraically simply by determining from the
literature the known Hammett sigma values for each substituent and
obtaining the algebraic sum thereof. Electron withdrawing substituents are
assigned negative sigma values. For example, in one preferred form R.sup.1
can be a phenyl group which is unsubstituted. The hydrogens attached to
the phenyl ring each have a Hammett sigma value of 0 by definition. In
another form, the phenyl nuclei can include halogen ring substituents. For
example, ortho- or para-chloro or fluoro substituted phenyl groups are
specifically contemplated, although the chloro and fluoro groups are each
mildly electron withdrawing.
Preferred phenyl group substituents are those which are not electron
withdrawing. For example, the phenyl groups can be substituted with
straight or branched chain alkyl groups (e.g., methyl, ethyl, n-propyl,
isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, tert-octyl, n-decyl,
n-dodecyl and similar groups). The phenyl groups can be substituted with
alkoxy groups wherein the alkyl moieties thereof can be chosen from among
the alkyl groups described above. The phenyl groups can also be
substituted with acylamino groups. Illustrative acylamino groups include
acetylamino, propanoylamino, butanoylamino, octanoylamino, benzoylamino
and similar groups.
In one particularly preferred form the alkyl, alkoxy and/or acylamino
groups are in turn substituted with a conventional photographic ballast,
such as the ballasting moieties of incorporated couplers and other
immobile photographic emulsion addenda. The ballast groups typically
contain at least eight carbon atoms and can be selected from both
aliphatic and aromatic relatively unreactive groups, such as alkyl,
alkoxy, phenyl, alkylphenyl, phenoxy, alkylphenoxy and similar groups.
The alkyl and alkoxy groups, including ballasting groups, if any,
preferably contain from 1 to 20 carbon atoms, and the acylamino groups,
including ballasting groups, if any, preferably contain from 2 to 21
carbon atoms. Generally, up to about 30 or more carbon atoms in these
groups are contemplated in their ballasted form. Methoxyphenyl, tolyl
(e.g., p-tolyl and m-tolyl) and ballasted butyramidophenyl nuclei are
specifically preferred.
Examples of specifically preferred hydrazine compounds disclosed in Simson
et al U.S. Pat. application Ser. No. 57,042 are the following:
##STR3##
Preferred photographic elements for use in the method of this invention
also include those in which the hydrazide comprises an adsorption
promoting moiety. Hydrazides of this type contain an unsubstituted or
mono-substituted divalent hydrazo moiety and an acyl moiety. The
adsorption promoting moiety can be chosen from among those known to
promote adsorption of photographic addenda to silver halide grain
surfaces. Typically, such moieties contain a sulfur or nitrogen atom
capable of complexing with silver or otherwise exhibiting an affinity for
the silver halide grain surface. Examples of preferred adsorption
promoting moieties include thioureas, heterocyclic thioamides and
triazoles. Exemplary hydrazides containing an adsorption promoting moiety
include:
1-[4-(2-formylhydrazino)phenyl]-3-methyl thiourea
3-[4-(2-formylhydrazino)phenyl]-5-(3-methyl-2-benzoxazolinylidene)rhodanine
-6-{[4-(2-formylhydrazino)phenyl]ureylene}-2-methylbenzothiazole
N-(benzotriazol-5-yl)-4-(2-formylhydrazino)phenylacetamide
N-(benzotriazol-5-yl)-3-(5-formylhydrazino-2-methoxyphenyl)propionamide
and
N-2-(5,5-dimethyl-2-thioimidazol-4-yl-idinimino)ethyl-3-[5-(formylhydrazin
o)-2-methoxyphenyl]propionamide.
Hydrazine compounds incorporated in the developing solution in the practice
of this invention are effective at very low levels of concentration. For
example, hydrazine gives effective results in the developing solution in
an amount of only 0.1 grams per liter. Hydrazine compounds incorporated in
the photographic element, as described in Simson et al U.S. Pat.
application Ser. No. 57,042, are typically employed in a concentration of
from about 10.sup.-4 to about 10.sup.-1 mole per mole of silver, more
preferably in an amount of from about 5.times.10.sup.-4 to about
5.times.10.sup.-2 mole per mole of silver, and most preferably in an
amount of from about 8.times.10.sup.-4 to about 5.times.10.sup.-3 mole per
mole of silver. The hydrazides containing an adsorption promoting moiety
can be used at a level as low as about 5.times.10.sup.-6 mole per mole of
silver.
The dihydroxybenzene developing agents employed in the aqueous alkaline
developing solutions of this invention are well known and widely used in
photographic processing. The preferred developing agent of this class is
hydroquinone. Other useful dihydroxybenzene developing agents include:
chlorohydroquinone,
bromohydroquinone,
isopropylhydroquinone,
toluhydroquinone,
methylhydroquinone,
2,3-dichlorohydroquinone,
2,5-dimethylhydroquinone,
2,3-dibromohydroquinone,
1,4-dihydroxy-2-acetophenone-2,5-dimethylhydroquinone,
2,5-diethylhydroquinone,
2,5-di-p-phenethylhydroquinone,
2,5-dibenzoylaminohydroquinone,
2,5-diacetaminohydroquinone,
and the like.
The 3-pyrazolidone developing agents employed in the aqueous alkaline
developing solutions of this invention are also well known and widely used
in photographic processing. Preferred developing agents of this class are
those represented by the formula:
##STR4##
in which R.sup.1 is aryl (including substituted aryl) and R.sup.2,
R.sup.3, and R.sup.4 are hydrogen or alkyl (including substituted alkyl).
Included within the definition of R.sup.1 are phenyl and phenyl
substituted with groups such as methyl, chloro, amino, methylamino,
acetylamino, methoxy and methylsulfonamidoethyl. Included within the
definition of R.sup.2, R.sup.3 and R.sup.4 are unsubstituted alkyl and
alkyl substituted with groups such as hydroxy, carboxy, or sulfo. The most
commonly used developing agents of this class are 1-phenyl-3-pyrazolidone,
1-phenyl-4,4-dimethyl-3-pyrazolidone,
1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone and
1-phenyl-4,4-dihydroxymethyl-3-pyrazolidone. Other useful 3-pyrazolidone
developing agents include:
1-phenyl-5-methyl-3-pyrazolidone,
1-phenyl-4,4-dimethyl-3-pyrazolidone,
1-p-aminophenyl-4-methyl-4-propyl-3-pyrazolidone,
1-p-chlorophenyl-4-methyl-4-ethyl-3-pyrazolidone,
1-p-acetamidophenyl-4,4-diethyl-3-pyrazolidone,
1-p-betahydroxyethylphenyl-4,4-dimethyl-3-pyrazolidone,
1-p-hydroxyphenyl-4,4-dimethyl-3-pyrazolidone,
1-p-methoxyphenyl-4,4-diethyl-3-pyrazolidone,
1-p-tolyl-4,4-dimethyl-3-pyrazolidone,
and the like.
The aqueous alkaline photographic developing compositions of this invention
contain a sulfite preservative at a level sufficient to protect the
developing agents against aerial oxidation and thereby promote good
stability characteristics. Useful sulfite preservatives include sulfites,
bisulfites, metabisulfites, and carbonyl bisulfite adducts. Typical
examples of sulfite preservatives include:
sodium sulfite,
potassium sulfite,
lithium sulfite,
ammonium sulfite,
sodium bisulfite,
potassium metabisulfite,
sodium formaldehyde bisulfite,
and the like.
In accordance with this invention, an amino compound is incorporated in the
aqueous alkaline developing solution in a contrast-promoting amount. This
use of an amino compound is based upon the discovery that high contrast
development in the presence of a hydrazine compound can be accomplished at
lower pH levels if the developer solution contains an adequate quantity of
an amino compound, as compared to the pH level needed to achieve the same
contrast without the use of the amino compound. The advantages of being
able to carry out development at lower pH levels will be readily apparent
to those skilled in the art of photographic processing. For example, with
the use of a lower pH level, the developing solution is much less
hazardous and its effective life is greatly enhanced.
The term "an amino compound," as used herein, is intended to refer to any
compound having amino functionality. Thus, compounds like o-aminobenzoic
acid and o-aminobenzyl alcohol are referred to herein as amino compounds
even though they might otherwise be referred to, respectively, as an acid
and an alcohol.
Amino compounds useful as contrast-promoting agents in accordance with this
invention are compounds of widely varying structure and properties. For
example, useful amino compounds include both inorganic amines, such as the
hydroxylamines, and organic amines. The organic amines can be aliphatic
amines, aromatic amines, cyclic amines, mixed aliphatic-aromatic amines,
or heterocyclic amines. Primary, secondary and tertiary amines, as well as
quaternary ammonium compounds, have all proven to be effective.
A preferred class of amino compounds are the alkanolamines, this term being
used herein to refer to an amine in which the nitrogen atom is directly
attached to a hydroxyalkyl radical, i.e., the amine comprises an >N--X--OH
group wherein X is alkylene. The radicals attached to the free bonds in
the >N--X--OH group can be hydrogen atoms or organic radicals, e.g.,
unsubstituted hydrocarbon radicals or substituted hydrocarbon radicals.
They are preferably hydrogen atoms or hydrocarbyl radicals of 1 to 12
carbon atoms, for example, alkyl, aryl, alkaryl or aralkyl radicals.
Particularly preferred alkanolamines for the purposes of this invention are
compounds of the formula:
##STR5##
wherein R.sup.1 is an hydroxyalkyl group of 2 to 10 carbon atoms and each
of R.sup.2 and R.sup.3 is a hydrogen atom, an alkyl group of 1 to 10
carbon atoms, an hydroxyalkyl group of 2 to 10 carbon atoms, a benzyl
radical, or a
##STR6##
group wherein n is an integer of from 1 to 10 and each of X and Y is a
hydrogen atom, an alkyl group of 1 to 10 carbon atoms, or an hydroxyalkyl
group of 2 to 10 carbon atoms.
A further preferred class of amino compounds are the alkyl amines,
especially those of the formula:
##STR7##
wherein R.sup.1 is an alkyl group of 1 to 10 carbon atoms and each of
R.sup.2 and R.sup.3 is a hydrogen atom or an alkyl group of 1 to 10 carbon
atoms.
Typical specific examples of the numerous amino compounds that can be used
in the practice of this invention include the following:
2-(2-Aminoethylamino)ethanol
Tetramethylammonium acetate
Choline
Choline Chloride
Hydroxylamine sulfate
Triethanolamine
Diethanolamine
Ethanolamine
Trimethylamine
2-Diethylamino-1-ethanol
2-Methylamino-1-ethanol
3-Dimethylamino-1,2-propanediol
3-Diethylamino-1-propanol
5-Amino-1-pentanol
Diethylamine
Methylamine
Triethylamine
Dipropylamine
Di-isopropylamine
3,3'-Diaminodipropylamine
3-Dimethylamino-1-propanol
Hydantoic Acid
Allylamine
Ethylamine
Dimethylamine
Ethylenediamine
2-Dimethylaminoethanol
2-Ethylaminoethanol
R.sub.1 --S--CH.sub.2 --CH.sub.2 --S--CH.sub.2 --CH.sub.2 --S--R.sub.1
2C.sub.7 H.sub.7 SO.sub.3.sup.-
R.sub.1 .dbd.(CH.sub.3).sub.2 N.sup.+ --CH CHOHCH.sub.2 --
Dimethylaminodecane-N-ammonium bromide
Ammonium Sulfate
2-[2-Aminoethylamino)-ethylamino]-ethanol
Aminoguanidine Sulfate
6-Aminohexanoic Acid
3-Amino-1-propanol
1-Dimethylamino-2-propanol
2-Hydroxy-4-thiadodecyl trimethyl ammonium pts
Pyridine
Glycine
o-Aminobenzoic Acid
Polyethyleneimine
L-(+)-Cysteine Hydrochloride
Benzylamine
2-Amino-1-ethanol
4-Amino-1-butanol
6-Amino-1-hexanol
1-(2-Aminoethyl)piperazine
1-(2-Hydroxyethyl)-4-(2-mercaptoethyl)-piperazine
2-(.beta.-Cyanoethylmercapto)-imidazolinium chloride
7,18-Diaza-6,19-dioxotetracosane-1,24-di(pyridinium perchlorate)
11-Amino Undeconoic Acid
DL-Serine
Morpholine
4-(2-Aminoethyl)morpholine
o-Aminobenzyl alcohol
Quinuclidine
1,4-Cyclohexanebis(methylamine)
The amino compounds differ markedly in their degree of effectiveness as
contrast-promoting agents. The less effective amines may have to be used
at relatively high concentrations to obtain the desired objective of high
contrast at a pH of above 10 and below 12.
The aqueous alkaline developing solutions of this invention can vary widely
in regard to the concentration of the various ingredients included
therein. Typically, the dihydroxybenzene developing agent is used in an
amount of from about 0.045 to about 0.65 moles per liter, more preferably
in an amount of about 0.09 to about 0.36 moles per liter; the
3-pyrazolidone developing agent is used in an amount of from about 0.005
to about 0.01 moles per liter, more preferably in an amount of from about
0.001 to about 0.005 moles per liter; the sulfite preservative is used in
an amount of from about 0.04 to about 0.80 moles per liter, more
preferably in an amount of from about 0.12 to about 0.60 moles per liter;
and the amino compound is used in an amount of from about 0.009 to about
0.85 moles per liter, more preferably in an amount of from about 0.009 to
about 0.35 moles per liter.
The aqueous alkaline developing solutions of this invention have a pH of
above 10 and below 12. To provide a pH in this range, the amino compound
which is utilized as a contrast-promoting agent can be employed in an
amount sufficient to establish the desired pH. Thus, the amino compound
can serve both the function of pH control and the function of promoting
the desired high contrast. However, since the amount of amino compound
required to give a pH of above 10 is relatively large, and may be far more
than the amount needed to provide the desired high contrast, it will often
be advantageous to incorporate another alkaline agent, such as an alkali
metal hydroxide, or carbonate, in the developing solution in an amount
that, together with the amino compound, establishes the desired pH of
above 10 and below 12. The preferred pH range for the aqueous alkaline
developing solutions of this invention is from 10.8 to 11.4.
In contrast with conventional "lith" developers which require a low level
of sulfite ion, the developing solutions of this invention can utilize
much higher levels of sulfite ion, and thereby achieve the advantage of
increased stability, since the higher level of sulfite ion provides
increased protection against aerial oxidation.
In carrying out the method of this invention, it is preferred to employ an
organic antifoggant to minimize fog formation. The organic antifoggant can
be incorporated in the photographic element or it can be added to the
developing solution, the essential requirement being that it be present
during the developing process. Particularly advantageous results are
achieved with the use of benzotriazole antifoggants. A further preferred
class of organic antifoggants are the mercapto azole antifoggants.
Inorganic antifoggants or restrainers, such as alkali metal bromides, can
be utilized in conjunction with the use of an organic antifoggant, if
desired.
Particularly preferred benzotriazole antifoggants for use in the developing
solutions of this invention are benzotriazole, halo-substituted
benzotriazoles such as 4-chlorobenzotriazole; 4-bromobenzotriazole and
5-chlorobenzotriazole, and alkyl-substituted benzotriazoles such as
5-methylbenzotriazole.
Preferred mercapto azole antifoggants are those represented by the formula:
##STR8##
wherein Z represents the atoms necessary to complete a 5 or 6 member
heterocyclic ring, such as pyrimidine, triazine, tetrazole, triazole,
imidazole, diazole, oxadiazole or thiadiazole ring; and SX represents a
mercapto function, n being a whole number, typically a number from 1 to
about 3, any free bonds being satisfied by hydrogen atoms. In the mercapto
function or group, X is a cation which includes hydrogen, an alkali metal,
e.g., sodium or potassium, ammonium or an organic amine residue of such
amines as triethyl amine, triethanol amine, morpholine and the like.
Mercapto tetrazole antifoggants are especially suitable in the practice of
this invention and include those of the formula:
##STR9##
wherein R is an aliphatic or aromatic radical containing up to about 30
carbon atoms and SX is a mercapto function.
Specific examples of mercapto azole antifoggants include:
mercapto-substituted pyrimidines such as:
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