Note: Descriptions are shown in the official language in which they were submitted.
1339297
BRIGHT SAFE LIGHT HANDT.~A~T.~ HIGH CONTRAST
PHOTOGRAPHIC MAT~RTAT~
This invention relates to negative acting silver
halide photographic materials capable of producing high
contrast silver images. In particular the invention
relates to high contrast photographic materials having a
reduced propensity to formation of pepper fog which are
also handleable under bright amber safelight conditions.
It is often desirable to produce black-and-white
photographic images formed by a combination of maximum
density areas and minimum density areas e.g. half tone
imaging. For such imaging applications a contrast of at
least 10 (herein referred to as high contrast) and more
typically near or above 20 is employed. An example of
high contrast photographic elements having white
reflective supports are phototypesetting materials
intended to produce black type character images on the
white background. An example of high contrast
photographic elements having transparent supports are lith
films, so called because they are used as contact
transparencies for exposing lithographic printing plates.
The illusion that some areas of a printed image are of
intermediate density is created by the viewer's inability
to resolve tiny dots of maximum density and background
areas of minimum density that separate them.
2 133~297
The use of hydrazines in the developer and/or
~ photographic elements of high contrast systems to increase
speed and contrast is well known and disclosed, for
example, in British Patent No. 598108, United States
Patents 2322027, 2419974, 2419975, 4166742, 4211857,
4224401, 4243739, 4272606, 4272614, 4311781 and 4323643
and in Research Disclosure, Vol. 235, November 1983, Item
23510.
In surface latent image forming silver halide
emulsions the grains which are exposed to light are
rendered developable while grains which are not exposed
to light are not intended to be developed. Nevertheless,
some of these unexposed grains develop spontaneously. In
full-tone imaging the spontaneously developing grains
raise minimum density more or less uniformly. Such
minimum density levels are referred to as fog and, so
long as they remain low, are not objectionable.
! Pepper fog differs from ordinary fog in that it takes
the form of small, maximum density areas randomly
distributed on a substantially uniform minimum density
background. When a photographic element exhibiting pepper
fog is viewed under magnification the impression to the
viewer is often that the magnified field of view has been
sprinkled with grains of pepper.
Pepper fog is a well recognised problem in high
contrast photographic systems and provides a serious
problem to the photographic printing plate making process.
These black spots are tiny black specks which appear in
1339297
the area between dots that is not intended to be developed
and tend to increase and grow on ageing of the
photographic material and particularly during storage
thereof under high temperature, high humidity conditions,
or as the concentration of the sulphite ion used commonly
as a preservative in the developer decreases or as the pH
value of the solution increases. The formation of black
peppers detracts considerably from the marketability of
the product as a photographic material for manufacturing
a photographic printing plate. Many efforts have been
made to overcome this black pepper problem but
improvement in black pepper is often accompanied by
decreases in sensitivity and gamma (contrast), and there
has been a strong demand for a photographic system
conducive to an improvement in black pepper which does
not entail losses of sensitivity and high contrast.
United States Patent Specification No. 4618574
discloses a negative working photographic element capable
of producing a high contrast silver image. The element
comprises surface latent image forming monodispersed
silver halide grains having a mean diameter of less than
0.7 microns a contrast enhancing arylhydrazide, and, in an
amount sufficient to reduce pepper fog while maintaining
high contrast, a polyhydroxybenzene and a carboxyalkyl-3H-
thiazoline-2-thione.
4 1339297
European Patent Publication No. 0196626 discloses a
silver halide photographic material comprising a support,
at least one silver halide emulsion layer and one or more
light-insensitive hydrophilic colloid layers, wherein said
silver halide emulsion layer or said light-insensitive
hydrophilic colloid layer contains a hydrazine derivative,
and the photographic material has a film surface pH not
higher than 5.8 on the side of said emulsion layer
inclusive of said light-insensitive hydrophilic colloid
layer. The formation of pepper fog is reduced by
maintaining the pH of the film surface on the side of the
emulsion layer to not more than 5.8.
U.S. Patent Specification No. 4,272,606 discloses the
construction of a photographic material having high
contrast and lower pepper fog which contains a hydrazine
together with a compound containing a thioamido moiety in
the molecule, included within this class are molecules
containing the rhodanine and thiohydantoin nucleus.
European Patent Publication No. 0285308 discloses
the use of water-soluble bromide and chloride compounds
e.g. alkali metal chlorides or bromides, added to a high
contrast silver halide photographic emulsion in
association with a hydrazine as a way of controlling
pepper fog and increasing contrast.
' 1339297
It is highly desirable in modern photographic
workshops to have a brightly lit environment and there is
a trend towards photosensitive materials which can be
handled under these conditions. The sensitivity of
materials which are handleable in bright amber light
conditions must be such that the sensitivity to
electromagnetic radiation does not extend much beyond
540nm. The natural sensitivity of silver halide emulsions
is such that they meet the criteria, for example silver
chloride absorbs little radiation above 440nm, silver
bromide above 500nm and a typical iodobromide emulsion
shows little sensitivity to radiation above 540nm.
However, when a material is constructed using spectrally-
unsensitised silver halide emulsion in combination with ahydrazine, although the requirements of sensitivity and
bright amber safelight handleability are met, there are
serious problems with the formation of pepper fog.
It has now been found that the presence of certain
monomethinebenzthiazole compounds provides high contrast
silver halide photographic emulsions with amber safelight
tolerance, and greatly reduced levels of pepper fog.
Therefore according to the present invention there
is provided a photographic element capable of producing a
high contrast silver image comprising a high contrast
negative-acting silver halide photographic emulsion in
association with a hydrazine characterised in that the
emulsion is additionally associated with a
monomethinebenzthiazole compound having a nucleus of the
1339297
general formula:
[~N~<N~Rn
11 12
ln whlch:
one of Rl and R2 represents an organlc group
contalnlng an acld functlon and the other ls selected from
hydrogen, an optlonally substltuted alkyl group and an
organlc group contalnlng an acld functlon, each R3 and R4 may
be the same or dlfferent and represents halogen, carboxyl,
1 c10 alkYl, cl-ClO-alkoxy~ Cl-Cl -alkYlthl~
or Cl-C10-alkoxycarbonyl or R3 and/or R4 may represent the
atoms necessary to complete a carbocycllc or heterocycllc
rlng whlch may be substltuted by halogen, carboxyl, hydroxy,
cyano, Cl-C10-alkyl, Cl-ClO-alkoxy, Cl-C10-alkylthlo or
Cl-C10-alkoxycarbonyl and each n lndependently represents 0,
1, 2, 3 or 4 wlth the provlso that the sllver hallde gralns
were not prepared ln the presence of an lrldlum salt.
It has been surprlslngly found that the addltlon of
a monomethlnebenzthlazole compound of formula (I)
slgnlflcantly reduces pepper fog formatlon ln hydrazlne-
contalnlng hlgh contrast photographlc emulslons. The
compound ls usually added ln an amount 10 5 to 3 x 10 1 mols
per mol of sllver hallde produclng a dramatlc reductlon ln
76747-10
D
1339297
6a
pepper fog formatlon. Thus lt ls readlly posslble to provlde
hlgh contrast photographlc elements whlch are handleable
under brlght amber safellght condltlons and have llttle
propensity to formatlon of pepper fog.
Although benzthlazole cyanlne dyes are well known
as spectral sensltlsers for sllver chlorobromlde of bromlde
emulslons, heretofore they have not been used as pepper fog
controllers ln hydrazlne contalnlng systems.
D 76747-lo
7 1339297
Canadian Patent No. 1146001 and U.S. Patent No.
4618574 disclose a list of useful spectral sensitising
compounds for high contrast hydrazine containing
materials. The preferred compounds are said to be
cationic cyanine and merocyanine dyes and are generally
ortho and panchromatic sensitisers. There is no
disclosure of the compounds of formula (I). U.S. Patent
No. 2410690 relates to a combination of a hydrazine
derivative and a cationic onium compound such as
cyclammonium quaternary salts or sulphonium salts to give
improved speed and contrast in photographic emulsion.
This Patent gives examples of the ways in which such a
system may be spectrally sensitised particularly to green
light and the use of the monomethine dyes, 3,3-
diethyloxacyanine iodide, 3,3'-diethyl-4,5,4',5'
dibenzothiacyanine iodide and l,l'-diethyl 2,2-cyanine
iodide among others is disclosed in this connection.
Although these compounds are structurally similar to the
compounds of formula (I) they were added solely to
increase the spectral sensitivity of the silver halide
material and there is no indication they have any activity
as pepper fog inhibitors. In the present invention
spectral sensitisation beyond about 500 nm is undesirable
since the coating is intended for safe handling under
bright orange lighting conditions.
1339297
Emulsions prepared in accordance with the invention
show essentially no sensitivity at wavelengths beyond 540
nm, and a slightly enhanced sensitivity to the blue
region. As a result, when imaged by a white-light source
they display a sensitivity that is only marginally less
than that of a conventional green-sensitised lith
emulsion, but their tolerance of amber safe-light is
greatly improved. In addition, the emulsions show
practically no pepper fog.
This desirable combination of effects appear to be
restricted to the narrow range of compounds defined by
formula (I). Thus monomethinebenzthiazoles similar to
compounds of formula (I) but lacking an acidic group on
and R2 do not control pepper fog. Likewise, benzoxazole
analogues of formula (I), with or without acid groups on
R1 or R2, do not control pepper fog.
The compounds of formula (I) may be present in a
silver halide photographic emulsion or may be incorporated
in layers other than the silver halide photographic
emulsion layer, such as a protective layer, interlayers, a
filter layer, etc. adjacent to the emulsion layer. It is,
however, preferred for the compound of formula (I) to be
incorporated in a surface latent image type silver halide
photographic emulsion layer together with the hydrazine
compound.
1339297
The amount of the compound of formula (I) added is
from 10-5 to 3 x 10-1, generally from 10-5 to 5 x 10-2
mole, per mole of silver contained in the silver halide
photographic emulsion layer associated with the compound,
but it is preferred to select the optimum content of the
compound depending on the grain size of silver halide
emulsion, the composition of the silver halide, the method
and degree of chemical sensitisation employed and the type
of hydrazine used. The method of testing for
sensitisation is well known to one skilled in the art and
can be easily accomplished.
To incorporate the dye of general formula (I) in a
silver halide layer or other layer, various well known
methods can be used. The compound may be added to an
aqueous solution of a hydrophilic colloid as a solution in
an organic solvent miscible with water, such as alcohols
e.g. methanol, ethanol, etc, and ketones e.g. acetone,
when the compound is oleophilic or as an aqueous solution
when the compound is hydrophilic. In adding the compound
it is sometimes convenient for dissolution to use an
alkaline aqueous solution, alternatively combinations of
solvent can be used.
In adding the compound of formula (I) to a silver
halide photographic material, the compound may be added
at any time between the start of chemical ripening and the
start of the coating process, but it is preferred to add
1339297
the compound after the end of the chemlcal rlpenlng of the
silver halide emulslon. It ls particularly preferred to add
the compound to the coatlng composltlon of a sllver hallde
photographlc emulslon prepared for coatlng.
The compound of formula (I) may posses one or more
rlng substltuents of the type known ln cyanlne dyes. As
mentloned above, the compounds are represented by the general
formula:
~ N ~ N ~ Rn
!1 12
ln whlch:
each n lndependently represents 0, 1, 2, 3 or 4,
each R3 and R4 may be the same or dlfferent and
represents a substltuent of the type known ln cyanlne dyes.
Exemplary substituents include halogen, carboxyl, hydroxy,
cyano, alkyl, alkoxy, alkylthio and alkoxycarbonyl, or groups
comprlsing comblnations of the above substltuents. The
carbon atom chalns of these substltuents generally contaln up
to 10 carbon atoms, preferably 1 to 5 carbon atoms.
~_~ 76747-10
L~
11 1339297
R3 and/or R4 may also represent the atoms necessary
to complete a carbocyclic or heterocyclic ring, which
itself may bear substituents selected from the above list.
At least one of R1 and R2 represents an organic group
containing an acid function e.g. alkylsulphonate,
alkylphosphate, alkyl carboxylate in which the alkyl
groups generally contain 1 to 10 carbon atoms, preferably
1 to 5 carbon atoms. The other of R1 and R2 may
additionally represent a hydrogen atom or an alkyl group,
generally of up to 10 carbon atoms, preferably 1 to 5
carbon atoms. The alkyl group may be substituted e.g.
with the substituents listed above with respect to R3 and
R4.
Preferred compounds for use in the invention include
those of the formula:
i< ~l~ R4
~3 1 1
in which R1 to R4 are defined above.
Specific examples of compounds of formula (III) are
shown in the following Table. They are readily prepared
by standard methods well-known in the cyanine dye art.
1339297
12
CcDqxYwnl Rl R2 R3 R4
No.
1 (CH2)2CHCH3So3~3 (CH2)2CHCH3S03(NH(C2H5)3) OCH3 OCH3
2 (CH2)2CHCH3S03~ (CH2)2CHCH3S03(NH(C2H5)3) Cl Cl
3 (CH2)3SO3~ C2H5 H H
4 (CH2)4SO3~ C2H5 H H
(CH2)2CHCH3so3~3 C2H5 SCH3 SCH3
The hydrazine compound present in the photographic
element may comprise hydrazine or any hydrazine derivative
capable of increasing speed and/or contrast of
photographic silver halide emulsions. Such compounds are
well known in the photographic art. In general suitable
hydrazines will have the general formula:
Rll ~R12
N-N
R14/ --R13
wherein:
Rll is an organic radical, and
R12, R13 and R14 each are hydrogen or an organic
radical.
Organic radicals represented by Rll, R12, R13 and R14
include hydrocarbon groups, such as an alkyl group, an
aryl group, an aralkyl group and an alicyclic group and
such groups can be substituted with substituents such as
alkoxy groups, carboxy groups, sulfonamido groups and
halogen atoms.
13 1339297
Other examples of hydrazine derivatives are
hydrazides, acyl hydrazines, semicarbazides,
carbohydrazides and aminobiuret compounds.
Hydrazine compounds suitable to be incorporated into
the photographic element according to the present
invention are disclosed in GB Patent Specification 598108
and in US Patent Specification 2419974; they include
the water soluble alkyl, aryl and heterocyclic hydrazine
compounds as well as the hydrazide, semicarbazide and
aminobiuret compounds.
A further class of hydrazine compounds, for use
according to this invention incorporated in the
photographic element, are the formylhydrazine compounds
~5 corresponding to the formula:
R15-NHNH-C-H
o
wherein:
R15 represents a substituted or unsubstituted
aromatic group.
Examples of aromatic groups represented by R15
include a phenyl group and a naphthyl group. Such
aromatic groups may be substituted with one or more
substituents which are not electron attracting, such as
straight or branched-chain alkyl groups (e.g. methyl,
ethyl, propyl, isopropyl, n-butyl, n-octyl, n-hexyl,
tert.-octyl, n-decyl, n-dodecyl, etc.), aralkyl groups
(e.g. benzyl, phenethyl, etc.), alkoxy groups (e.g.
methoxy, ethoxy, 2-methyl-propyloxy, etc.), amino groups
1339297
14
which are mono, or disubstituted with alkyl groups
acylaminoaliphatic groups (e.g. acetylamino,
benzoylaminoetc.), as disclosed in US Patent 4168977 and
in CA Patent 1146001. Such aromatic groups may also be
substituted with a ureido group of formula:
o
R16-N_C_N_
l l
R17 R18
wherein:
R16 and R17 (which may be same or different) each
represents hydrogen, an aliphatic group (such as a
straight or branched-chain alkyl group, a cycloalkyl
group, a substituted cycloalkyl group, an alkenyl group
and an alkynyl group), an aromatic group (such as a phenyl
group and a napthyl group) or a heterocyclic group;
R18 represents hydrogen or an aliphatic group (such
as those listed above as described in US Patent 4323643.
Other hydrazine compounds, for use according to this
invention incorporated in the photographic element, are
those represented by the formula:
Rl9-NHNH-C-R20
o
wherein:
R19 represents the same aromatic group of the formula
above, and
R20 represents an alkyl group having 1 to 3 carbon
atoms, which may be a straight or branched-chain alkyl
(e.g. methyl, ethyl, n-propyl and isopropyl) or a phenyl
group. The phenyl group may be substituted with one or
1339297
- 15
more substituents which preferably are electron attracting
groups, such as halogen atoms (chlorine, bromine, etc.), a
cyano group, a trifluoromethyl group, a carboxy group or a
sulfo group, etc. Specific examples of hydrazine
compounds represented by the formula above are disclosed
in US Patent Specification 4224401.
Still other examples of hydrazine compounds, for use
according to this invention incorporated in the
photographic element, are those corresponding to the
lo formula:
,'Z"
~--N ~y) ~ C -
')I O
wherein:
R21 represents hydrogen, an aliphatic group which may
be substituted;
Y represents a divalent linking group;
m represents 0 or l,
W represents a divalent aromatic group (such as for
example a phenylene group, a naphthylene group and the
analogous substituted groups thereof);
R22 represents a hydrogen atom, an aliphatic group
which may be substituted and Z represents the non-metallic
atoms necessary to form a 5- or 6-membered heterocyclic
1339297
16
ring. Specific examples of hydrazine compounds
represented by the formula above are disclosed in US
Patent 4272614.
In one particular form the hydrazine compound to be
incorporated in the photographic element is substituted
with ballasting groups, such as the ballasting groups of
incorporated colour couplers and other non-diffusing
photographic emulsion addenda. Said ballasting groups
contain at least 8 carbon atoms and can be selected from
the relatively non-reactive aliphatic and aromatic groups
such as alkyl, alkoxy, alkylphenyl, phenoxy, alkylphenoxy
groups and the like.
Such hydrazine compounds can be incorporated in the
photographic element using various methods well-known in
the photographic art, the most common being the method of
dissolving the hydrazine derivatives in a high boiling
solvent and dispersing the mixtures in the emulsion, as
described for example in US Patent 2322027.
A preferred class of hydrazines suitable for use in
the invention as disclosed in European Patent Publication
No. 253665 and are of the general formula:
R23-NR24-NR25-G-X (IV)
in which:
R23 represents an aryl group,
one of R24 and R25 is a hydrogen and the other is
selected from hydrogen, arylsulphonyl and trifluoroacetyl,
G represents carbonyl, sulphonyl, sulphoxy,
phosphoryl, or an N-substituted or unsubstituted imino
group and,
1339297
17
X is hydrogen, alkyl, aryl or a moiety such that at
a pH in the range of 9.5 to 12.5 in the presence of an
oxidised hydroquinone a cyclisation reaction takes place
cleaving the moiety -G-X from the remainder of the molecule
and forming a cyclic structure comprising atoms of the moiety
-G-X.
The hydrazine compound is incorporated in the
photographic element, for example in a silver halide emulsion
layer or in a hydrophilic colloidal layer, preferably a
hydrophilic colloidal layer 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 the emulsion and the hydrophilic colloidal
layers, such as one or more of a subbing layer, interlayers
and protective layers.
The hydrazines may be added to the silver halide
photographic emulsion at any desired period from the
initiation of chemical ripening to before coating, but it is
preferred to add the compound after finishing chemical
ripening. It is particularly preferred to add the compound to
a coating composition prepared for coating.
Hydrazines of formula (V) may be incorporated as
microcrystalline dispersions. In these cases, no water-
immiscible solvent is used in the preparation of the gelatin
dispersions.
76747-10
e -' ' ~'~
1339297
18
It is preferred that the hydrazine be incorporated in
an amount of from 10-6 mol to lo~l mol, and preferably
from 10-5 mol to 5 x 10-2 mol per mol of silver halide
but it is desirable to select the optimum amount of the
compound according to the grain size of silver halide
emulsion, the halogen composition, the manner and extent
of chemical sensitization, and the kind of antifoggant
compounds. The most appropriate compound and amount
thereof for a particular use can be easily selected by
general tests well known to persons skilled in the art.
It is preferred that silver halide grains used for at
least one silver halide emulsion layer in this invention
be of substantially surface latent image type.
The silver halide emulsion used in the invention may
comprise any of silver chloride, silver chlorobromide,
silver iodobromide, silver iodochlorobromide, etc., but
preferably contains at least 60 mol% silver bromide. The
iodide content is preferably not more than 10 mol% and
more desirably is in the range of from 0.1 to 5 mol~.
In regard to the average grain size of silver halide
used in accordance with this invention, fine grains (for
example, 0.7 micron or less) are preferable, and very fine
grains of average diameter not larger than 0.5 micron are
particularly preferable. While the choice of grain size
distribution is optional, a monodispersion is preferable.
The term "monodispersion" as used herein means that,
whether in weight or in number, at least 95% of grains are
sized within +40% of the mean grain size.
1339297
The silver halide grains in the photographic emulsion
may be regular crystals such as cubes or octahedra, or
irregular crystals such as spheres or plates (tabular
grains), or composites.
Each of the silver halide grains may be made up of a
uniform phase through its core and surface layer, or may
be dissimilar in phase between the core and the surface.
It is also possible to use two or more independently
prepared silver halide emulsions as a mixture.
In the course of formation of silver halide grains or
in the process of physical ripening, there may be added to
the silver halide emulsion a cadmium salt, ruthenium, lead
salt, thallium salt, rhodium salt or rhodium complex salt,
iridium salt or iridium complex salt, or the like.
Gelatin is preferably used as the binder or protective
colloid for the photographic emulsion, but other
hydrophilic colloids can also be employed, for example,
gelatin derivatives, graft copolymers of gelatin to other
high polymers, proteins such as albumin and casein,
cellulose derivatives such as hydroxyethyl cellulose,
carboxymethyl cellulose, cellulose sulphate esters, etc.,
sugar derivatives such as sodium alginate, starch
derivatives, etc., and synthetic homo- or copolymers such
as polyvinyl alcohol, partially acetalized polyvinyl
alcohol, poly-N-vinylpyrrolidone, polyacrylic acid,
polymethacrylic acid, polyacrylamide, polyvinylimidazole
and polyvinylpyrazole.
1339297
The silver halide emulsion may be chemically
sensitized. Known methods of chemical sensitization of
silver halide emulsions include sulphur sensitization,
reduction sensitization and noble metal sensitization, and
the chemical sensitization may be effected by any or a
combination of such methods.
The usual method of the noble metal sensitization is
gold sensitization and for this purpose a gold compound
generally a complex salt of gold, is utilized. Complex
salts of other noble metals such as platinum, palladium,
rhodium, etc., may be additionally contained. Examples of
this method are described in U.S. Patent 2448060 and
British Patent 618061.
Sulphur sensitizers include, in addition to sulphur
compounds contained in gelatin, various sulphur compounds
such as thiosulphates, thiourea compounds, thiazoles, and
rhodanines.
Reduction sensitizers include stannous salts,
amines, formamidinesulphinic acid, silane or borane
compounds and the like.
The photographic elements may include a variety of
compounds for the prevention of fog during production,
storage or photographic processing or for the purpose of
stablising its photographic qualities. Thus, for example,
there may be added the compounds referred to commonly as
antifoggants or stabilizers, for example various azole
compounds such as benzothiazolium salts, nitroimidazoles,
chlorobenzimidazoles, bromo-benzimidazoles,
mercaptothiazoles, mercaptobenzothiazoles,
1339297
21
mercaptotetrazoles, mercaptothiadiazoles, aminotriazoles,
benzothiazoles, nitrobenzothiazoles, etc.;
mercaptopyrimidines, thioketo compounds such as
oxazolylthione, etc.; azaindenes such as triazaindene,
teraazaindenes (particularly, 4-hydroxy-substituted-
(1,3,3a,7)tetraazaindenes), pentaazaindenes, etc.
benzenesulphinic acid, benzenesulphonamide, etc. Amongst
these compounds, benzotriazoles (e.g., 5 methylbenzo
triazole) and nitroindazoles (e.g., 5-nitroindazole) are
preferred. These compounds may also be incorporated in
the processing solution.
The photographic elements may contain inorganic or
organic hardening agents in the photographic emulsion
layer or other hydrophilic colloid layer. For this
purpose, chromium salts (chrome alum, chromium acetate,
etc.), aldehydes (formaldehyde, glyoxal, glutaraldehyde
etc.), N-methylol compounds (dimethylolurea,
methyloldimethylhydantoin, etc.), dioxane derivatives
(2,3-dihydroxydioxane, etc.), active vinyl compounds
(1,3,5 triacryloyl-hexahydro-s-triazines, 1,3,-vinyl-
sulphonyl-2-propanol, etc.), active halogen compounds
(2,4-dichloro-6-hydroxy-s-triazine, etc.), mucohalogenic
acids (mucochloric acid, mucophenoxy-chloric acid, etc.),
and the like may be used. These hardening agents may be
incorporated alone or in combination.
In the photographic emulsion layer or other
hydrophilic colloid layer in the photographic material
produced in accordance with this invention, a variety of
surface active agents may be incorporated for various
22 1 33929 7
purposes such as improvement of coating properties
antistatic properties slipping properties, emulsion
dispersibility, anti-adhesion properties, and
photographic properties (for example, development
acceleration, increase in contrast, sensitization, etc.).
Examples of nonionic surfactants are saponin,
alkylene oxide derivatives e.g., polyethylene glycol,
polyethylene glycol/polypropylene glycol condensate,
polyethylene glycol alkyl ethers, polyethylene glycol
alkyl aryl ethers, polyethylene glycol esters,
polyethylene glycol sorbitan esters, polyalkylene glycol
alkylamines or amides, silicone polyethylene oxide
adducts), glycerol derivatives (e.g., alkenylsuccinic acid
polyglyceride, alkylphenol polyglyceride), polyhydric
alcohol-fatty acid esters, sugar alkyl esters, etc..
Anionic surfactants containing acid groups such as a
carboxy group, a sulpho group, a phospho group, a
sulphuric acid ester group, a phosphoric acid ester group,
etc., for example alkylcarboxylates, alkylsulphonates,
alkylbenzenesulphonates, alkylnaphthalenesulphonates,
alkylsulphuric acid esters, alkylphosphoric acid esters
N-acyl-N-alkyltaurines, sulphosuccinic acid esters,
sulphoalkylpolyoxyethylene alkylphenyl ether,
polyoxyethylene alkylphosphoric acid esters, etc.;
amphoteric surfactants such as amino acids,
aminoalkylsulphonic acids, aminoalkylsulphuric or
phosphoric acid esters, alkylbetaines, amine oxides etc.,
may also be used. Cationic surfactants such as
alkylamines, aliphatic or aromatic quaternary ammonium
1339297
23
salts, heterocyclic quaternary ammonium salts such as
pyridinium salts, imidazolium salts, etc., aliphatic or
heterocyclic ring-containing phosphonium or sulphonium
salts, etc. may be included.
In the photographic emulsion layer or other
hydrophilic colloid layer of the photographic material
according to this invention, matting agents such as
silica, magnesium oxide, polymethylmethacrylate, etc., may
be incorporated for the purpose of preventing adhesion.
lo The support of the photographic element may be made
of cellulose triacetate, cellulose diacetate,
nitrocellulose, polystyrene, polyethylene terephthalate or
the like. However, the use of polyethylene terephthalate
is particularly useful.
Suitable developer compositions for use in the
invention are any of those known in the art for
development of hydrazine containing rapid access lith
films and will generally have a pH in the range 9.5 to
12.5.
Thus, the silver halide photographic elements provide
a sufficient ultra-high contrast negative image using a
developer containing at least 0.15 mol/litre of sulphite
ion as a preservative, and having a pH value in the range
of from 10.5 to 12.3 and particularly preferably in the
range of from 11.0 to 12.3.
1339297
24
There is no particular limitation on the developing
agents than can be employed in the method of this
invention. Thus, for example, dihydroxybenzenes (e.g.,
hydroquinone), 3-pyrazolidones (e.g., 1-phenyl-3-
pyrazolidone, 4,4-dimethyl-1-phenyl-3-pyrazolidone),
aminophenols (e.g., N-methyl-p-aminophenol), etc., can be
used alone or in combination.
The silver halide photographic element is especially
suitable for processing with a developer containing a
dihydroxybenzene compound as the developing agent and a 3-
pyrazolidone compound or an aminophenol compound as the
auxiliary developing agent. The preferred concentrations
of these compounds in the developer are from 0.05 to 0.5
mol/litre for the dihydroxybenzene, and 0.06 mol/litre or
less for 3-pyrazolidone or aminophenol.
As described in US Patent 4269929, amine compounds
may be added to the developer to thereby increase the rate
of development thereby reducing development time.
In addition to the foregoing compounds, there may be
added to the developer other additives including pH
buffers such as sulphites, carbonates, borates, and
phosphates of alkali metals, development restrainers or
antifoggants such as bromides, iodides and organic
antifoggants (preferably nitroindazoles and
benzotriazoles). If desired, water softeners
solubilizing agents or cosolvents, toners, development
1339297
accelerators, surfactants (preferably aforesaid
polyalkylene oxides), antifoams, hardeners, and silver
stain inhibitors (e.g., 2-mercapto-
benzimidazolesulphonic acids) may also be incorporated in
the developer.
As a fixing bath, a solution of the conventional
composition may be employed. Thiosulphates, thiocyanates,
and those organic sulphur compounds which are generally
known to be effective fixing agents can be used as fixing
agents in the bath. The fixing bath may contain a water
soluble salt of aluminium or the like as a hardener.
A stop bath e.g. 1% acetic acid solution, may be
employed. The processing temperature is generally
selected within the range of from 18~C to 50~C.
For photographic processing, an automatic developing
machine is desirably used, and a sufficient ultrahigh
contrast negative image can be obtained even with a
processing time, i.e., the time for entry of the
photographic material into the machine to exit from the
machine of from 90 to 120 seconds.
26 1339Z9
The invention will now be illustrated by the
following Example.
EXAMPLE
A silver halide emulsion having halide mole
percentage ratio of 68:30:2 of Br:Cl:I was prepared by a
conventional double jet technique under constant pAg
conditions. The resulting emulsion had a narrow grain
size distribution with an average size of 0.25 microns.
The emulsion was then coagulated and washed being
reconstituted to 95g gelatin per mole of silver.
The emulsion was chemically sensitised with sodium
thiosulphate in the conventional fashion. Additions were
also made before coating onto subbed polyester base, a
monomethine benzothiazole as reported in the following
Table, and then an anionic wetting agent (Hostapur SAS93)
(lOml of 10% solution), polyoxyethylene cetyl ether
(surfactant) (150ml of 1% solution), a contrast promoting
agent (benzhydrol) (30ml of 5% solution in methanol) and a
hydrazine derivative (3g):
o
~ C 4llq
c~2
(All quantities are per mole of silver).
1339297
The order of addition was not critical but preferably
the monomethine benzothiazole was added first. The
emulsion was coated at a silver coating weight of 3.5g
per square metre.
A gelatin topcoat was applied comprising 50g gelatin
per lOOOg water, wetting agent, matting agent (silica),
and a hardener (2-hydroxy-4,6-dichloro-1,3,5-triazine).
Samples of the film were then exposed in a
sensitometer to light from a tungsten filament lamp
attenuated by a 0 to 1.5 continuous neutral density wedge
in contact with the coating. The coatings were then
developed for 30 seconds at 38~C in a developer of the
following composition:
Water 1800 g
15 Potassium hydroxide ls5 g
Potassium metabisulphite 124 g
Diethylenetriaminepentaacetic
acid 5Na 10 g
Pyruvic acid sodium salt 7.5 g
20 Hydroquinone 60 g
Metol 5.0 g
5-Methylbenzotriazole 0.2 g
Potassium bromide 9.25 g
Potassium chloride 2.7 g
25 Phosphoric acid (85%) 90 g
Final volume2.0 litres pH 11.0
l339297
28
After development the samples were fixed, washed and
dried. Sensitometric characteristics are given below
together with an assessment of pepper fog.
Dot quality was assessed by making an exposure using
a tungsten filament lamp through a Kodak "Ultratec"
contact halftone screen held in contact with the film
sample by a vacuum frame, and processing as before.
Dot quality was measured microscopically on an
evaluation scale of 1 (highest quality) to 5 (lowest
quality). Scores of 2 or below indicate that the product
has valuable commercial properties. A score of 3
indicates that the product is of moderate quality but is
marginally usable. As score of 4 or higher indicates
unacceptability.
29 1339237
~ .~
~ ~ C
~ g I .
r ~ ~
V
~ O
O Ul
B ~,
~ VJ 1 rl~
~3 0
~- 3
N ~ ~ P d;~
1339297
It can be seen that the addition of the monomethine
benzthiazole derivative in accordance with the invention
gives a high sensitivity high contrast film showing little
sign of pepper fog.
As comparative examples the following compounds were
also separately incorporated into the system at the same
concentration in place of the components of formula (I).
S--~ C7H7S03(~
C~3 CH3
11 ~3_Gi/>~< N 1~ C7H7S03
CH3 3
i~ 7 >~< N~¢~ 3 C1~3
CH3 3
The addition of compounds A, B and C resulted in the
level of pepper fog in the exposed and processed films to
be so high that reliable sensitometric data could not be
obtained. These examples illustrate the importance of
nature of the groups Rl and R2 in the compounds of formula
(I) and that benzoxazole compounds are not effective in
limiting the amount of pepper fog obtained.
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