 |
Description  |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to silver halide photographic light-sensitive
materials and, more particularly, to photographic light-sensitive
materials providing extremely contrasty negative image photographic
characteristics.
2. Description of the Prior Art
A method of obtaining photographic characteristics of a contrasty negative
image by adding a hydrazine compound to a silver halide photographic
emulsion is described in U.S. Pat. No. 2,419,975. U.S. Pat. No. 2,419,975
discloses that extremely contrasty photographic characteristics, such as a
gamma (.gamma.) of more than 10, can be obtained by adding a hydrazine
compound to a silver chlorobromide emulsion and developing the emulsion
with a developer having a pH as high as 12.8. However, strongly alkaline
developers having a pH near 13 are so unstable that they tend to be
oxidized by air and, therefore, cannot be used or stored for long periods
of time. Moreover, development at such a high pH tends to cause fog.
Ultra-contrasty photographic characteristics, either of a negative image or
of a positive image, are very useful for the photographic reproduction of
an image of a continuous tone comprising a dot image which is useful in
making printing plates or the reproduction of a line image. For the above
purposes, hitherto a method of using a silver chlorobromide photographic
emulsion having a silver chloride content of more than 50 mol%, preferably
more than 75 mol%, and developing the emulsion with a hydroquinone
developer having an extremely reduced effective concentration of sulfite
ions (usually less than 0.1 mol/l) has been generally adopted. However, in
this method, since the sulfite ion in the developer is in low
concentration, the developer is very unstable and cannot withstand storage
for a period exceeding 3 days. Furthermore, since a silver chlorobromide
emulsion containing a relatively high percentage of silver chloride must
be used, high sensitivity cannot be obtained.
Accordingly, use of an emulsion of high sensitivity and a stable developer
to obtain ultra-contrasty photographic characteristics useful for the
reproduction of a dot image or a line image have been strongly desired.
SUMMARY OF THE INVENTION
A first object of this invention is to provide silver halide photographic
materials which can be processed with a stable developer to provide
photographic characteristics of an extremely contrasty negative image.
A second object of this invention is to provide highly sensitive silver
halide photographic light-sensitive materials which can provide
photographic characteristics of an extremely contrasty negative image.
A third object of this invention is to provide silver halide photographic
light-sensitive materials which can provide photographic characteristics
of an extremely contrasty negative image with less fog being produced.
The above various objects of this invention are accomplished by using a
silver halide photographic light-sensitive material containing at least
one negative image silver halide photographic emulsion layer comprising
silver halide grains which have an average grain size of not more than
about 0.7.mu. and which are substantially of the surface latent image type
and containing a binder in an amount of not more than about 250 g per mol
of silver halide and in which a compound represented by the following
general formula (I):
r.sup.1 nhnhcor.sup.2 (i)
wherein R.sup.1 represents an aryl group; and R.sup.2 represents a hydrogen
atom, a phenyl group or an unsubstituted alkyl group having 1 to 3 carbon
atoms; is present in at least one of the hydrophilic colloid layers and a
compound represented by the following general formula (II) or (III):
##STR3##
wherein Y represents a sulfur atom, a selenium atom, an oxygen atom, a
nitrogen atom or a divalent residue: --NR.sup.4 --, wherein R.sup.4
represents a hydrogen atom, an alkyl group or an aryl group; Z represents
an atomic group required for completing a 5- or 6-membered heterocyclic
ring; R.sup.5 and R.sup.6, which may be the same or different, each
represents a hydrogen atom, a halogen atom, a carboxy group, an
alkoxycarbonyl group, an alkyl group, an aryl group, a hydroxy group, a
mercapto group or an alkylthio group or R.sup.5 or R.sup.6 may combine and
represent an atomic group required for forming a 5- or 6-membered ring; m
is 0 or 1, m being 0 where Y represents a sulfur atom, a selenium atom or
an oxygen atom; and R.sup.3 represents a hydrogen atom, an
alkylthiocarbonyl group or a moiety of the formula:
##STR4##
wherein Y, Z, R.sup.5, R.sup.6 and m are each as described above; is
present in the same or a different hydrophilic colloid layer.
DETAILED DESCRIPTION OF THE INVENTION
In the general formula (I) above, R.sup.1 represents a monocyclic or
bicyclic aryl group. A suitable example of a monocyclic aryl group for
R.sup.1 is a phenyl group and a suitable example of a bicyclic aryl group
for R.sup.1 is a naphthyl group. The aryl group may be substituted with
one or more substituents which are not electron-attracting, such as alkyl
groups having 1 to 20 carbon atoms (which may be straight or branched
chained, e.g., methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,
n-octyl, n-hexyl, tert-octyl, n-decyl, n-dodecyl, etc.), aralkyl groups
having 1 to 3 carbon atoms in the alkyl moiety thereof (e.g., benzyl,
phenethyl, etc.), alkoxy groups having 1 to 20 carbon atoms (in which the
alkyl moiety may be straight or branched chain, e.g., methoxy, ethoxy,
2-methylpropyoxy, etc.), amino groups which are mono- or disubstituted
with alkyl groups having 1 to 20 carbon atoms, aliphatic acylamino groups
having 2 to 21 carbon atoms or aromatic acylamino groups (e.g.,
acetylamino, octynylamino, benzoylamino, dimethylamino, etc.), etc.
R.sup.2 represents a hydrogen atom, an alkyl group having 1 to 3 carbon
atoms which may be straight or branched chained (e.g., methyl, ethyl,
n-propyl and isopropyl) or a phenyl group. It is preferred for the alkyl
group to be unsubstituted. The phenyl group may be substituted with one or
more substituents which preferably are electron-attracting groups, such as
a halogen atom (chlorine or bromine, etc.), a cyano group, a
trifluoromethyl group, a carboxyl group or a sulfo group, etc.
Specific examples of suitable substituents represented by R.sup.1 are a
phenyl group, an .alpha.-naphthyl group, a .beta.-naphthyl group, a
p-tolyl group, an m-tolyl group, an o-tolyl group, a p-methoxyphenyl
group, an m-methoxyphenyl group, a p-dimethylaminophenyl group, a
p-diethylaminophenyl group, a p-(acetylamino)phenyl group, a
p-(capryloylamino)phenyl group, a p-(benzoylamino)phenyl group and a
p-benzylphenyl group.
Specific examples of suitable substituents represented by R.sup.2, other
than a hydrogen atom, are a methyl group, an ethyl group, an n-propyl
group, an isopropyl group, a phenyl group, a 4-chlorophenyl group, a
4-bromophenyl group, a 3-chlorophenyl group, a 4-cyanophenyl group, a
4-carboxyphenyl group, a 4-sulfophenyl group, a 3,5-dichlorophenyl group
and a 2,5-dichlorophenyl group.
The substituent represented by R.sup.1 is preferably a monocyclic aryl
group, and particularly preferred are an unsubstituted phenyl group and a
tolyl group.
The substituent represented by R.sup.2 is preferably a hydrogen atom, a
methyl group or a phenyl group which may be substituted. A hydrogen atom
is particularly preferred for R.sup.2.
In the above general formulas (II) and (III), Y represents a sulfur atom, a
selenium atom, an oxygen atom, a nitrogen atom or a divalent residue:
--NR.sup.4 --. R.sup.4 represents a hydrogen atom, an alkyl group or an
aryl group. Z represents an atomic group required for completing a 5- or
6-membered heterocyclic ring. R.sup.5 and R.sup.6, which may be the same
or different, each represents a hydrogen atom, a halogen atom (such as a
chlorine atom, a bromine atom, etc.), a carboxy group, an alkoxycarbonyl
group, an alkyl group, an aryl group, a hydroxy group, a mercapto group or
an alkylthio group or R.sup.5 and R.sup.6 may combine and represent an
atomic group required for forming a 5-membered or 6-membered ring. m is 0
or 1, with m being 0 where Y represents a sulfur atom, a selenium atom or
an oxygen atom. R.sup.3 represents a hydrogen atom, an alkylthiocarbonyl
group, an alkoxycarbonyl group, an aryloxycarbonyl group, an
alkoxycarbonylmethyl group, an aryloxycarbonylmethyl group or a moiety of
the formula:
##STR5##
wherein Y, Z, R.sup.5, R.sup.6 and m are as described above.
Examples of suitable 5- or 6-membered heterocyclic rings completed by Z are
those containing one or more hetero atoms such as a sulfur atom, a
nitrogen atom, an oxygen atom or a selenium atom, preferably a sulfur
atom, a nitrogen atom or an oxygen atom. Specific examples of heterocyclic
rings completed by Z include a thiazole ring, a selenazole ring, an
oxazole ring, an imidazole ring, a pyrazole ring, a 1,3,4-thiadiazole
ring, a 1,3,4-oxadiazole ring, a 1,2,4-thiadiazole ring, a 1,3,4-triazole
ring, a tetrazole ring, a pyrimidine ring, a 1,3,5-triazine ring and a
1,2,3-triazine ring. These heterocyclic rings, of course, include those
which are condensed with a 5- to 7-membered carbon ring or heterocyclic
ring. That is, the thiazole ring includes, e.g., a benzothiazle nucleus, a
naphthothiazole nucleus, a dihydronaphthothiazole nucleus, a
tetrahydrobenzothiazole nucleus, etc. The selenazole ring includes, e.g.,
a benzoselenazole nucleus, etc. The oxazole ring includes, e.g., a
benzoxazole nucleus, a naphthoxazole nucleus, etc. The imidazole ring
includes, e.g., a benzimidazole nucleus, an imidazolopyrimidine nucleus,
etc. The triazole ring includes, e.g., a triazolopyridine nucleus, a
triazolopyrimidine nucleus, etc. The pyrazole ring includes, e.g., a
pyrazolopyridine nucleus, a pyrazolo-pyrimidine nucleus, etc. The
pyrimidine ring includes, e.g., a pyrazolopyrimidine nucleus, a
pyrrolopyrimidine nucleus, a triazolopyrimidine nucleus, etc.
The carbon atoms of these heterocyclic rings can contain various
substituents. Examples of suitable substituents are an alkyl group having
1 to 20 carbon atoms (such as a methyl group, an ethyl group, an n-butyl
group, a t-butyl group, a heptyl group or a heptadecyl group), an alkoxy
group having 1 to 20 carbon atoms (such as methoxy group, an ethoxy group,
a dodecyloxy group or a heptadecyloxy group), an alkylthio group having 1
to 20 carbon atoms (such as a methylthio group, an ethylthio group or a
butylthio group), a hydroxy group, a mercapto group, an amino group (which
may be unsubstituted or substituted, e.g., an alkyl-substituted amino
group such as a dimethylamino group, a methylamino group, a diethylamino
group, a butylamino group or a benzylamino group; an aryl-substituted
amino group such as an anilino group or a diphenylamino group; an
acylamino group such as an acetylamino group, a capryloylamino group, a
benzoylamino group, a methylsulfonylamino group, a benzenesulfonylamino
group or a p-toluenesulfonylamino group; a thioamido group such as an
acetylthioamido group or a propionylthioamido group; etc.), an aryl group
(such as a phenyl group, a naphthyl group or a tolyl group), an alkenyl
group having 2 to 20 carbon atoms (such as an allyl group or a methallyl
group), an aralkyl group having an alkyl moiety with 1 to 4 carbon atoms
(such as a benzyl group or a phenethyl group), a halogen atom (such as a
chlorine atom or a bromine atom), a cyano group, a carboxyl group, a sulfo
group, a carbamoyl group (which may be substituted, e.g., a carbamoyl
group, a methylcarbamoyl group, a dimethylcarbamoyl group, an
ethylcarbamoyl group, a phenylcarbamoyl group, etc.), a thiocarbamoyl
group (which may be substituted, e.g., a thiocarbamoyl group, a
methylthiocarbamoyl group, a dimethylthiocarbamoyl group, an
ethylthiocarbamoyl group, a phenylthiocarbamoyl group, etc.), an
alkoxycarbonyl group having 2 to 22 carbon atoms (such as a
methoxycarbonyl group, an ethoxycarbonyl group or a butoxycarbonyl group),
an aryloxycarbonyl group (such as a phenoxycarbonyl group), an
alkylcarbonyl group having 2 to 22 carbon atoms (such as an acetyl group
or a capryloyl group) and an oxygen atom. The above-described alkyl group
may be further substituted with one or more of a carboxy group, a sulfo
group, an alkoxycarbonyl group (such as a methoxycarbonyl group or an
ethoxycarbonyl group), an acyloxy group (such as an acetoxy group), an
aryl group (e.g., an unsubstituted or substituted phenyl group such as a
nitrophenyl group), etc.
The substitutable nitrogen atom of the above-described heterocyclic rings
can be substituted with substituents as described above for R.sup.4.
Where Y represents --NR.sup.4 --, the alkyl group represented by R.sup.4
has 1 to 20 carbon atoms, and includes unsubstituted and substituted alkyl
groups. The alkyl group may be substituted with one or more of the
following substituents, e.g., a halogen atom, a cyano group, a carboxy
group, a sulfo group, a sulfato group, a phospho group, a carbamoyl group,
an aminosulfonyl group, a hydroxy group, an alkoxy group having 1 to 20
carbon atoms [e.g., a methoxy group, an ethoxy group, a propoxy group, a
butoxy group; an alkoxy group substituted with, e.g., a hydroxy group, an
alkoxy group having 1 to 6 carbon atoms (such as a methoxy group, an
ethoxy group or a propoxy group), an acyloxy group having 2 to 8 carbon
atoms (such as an acetoxy group or a propionyloxy group), a sulfo group, a
sulfoalkoxy group having 1 to 6 carbon atoms (such as a 2-sulfoethoxy
group or a 3-sulfopropoxy group), etc.], an acyloxy group having 2 to 22
carbon atoms (such as an acetoxy group or a propionyloxy group), an
alkenyl group having 2 to 22 carbon atoms (such as a vinyl group), an
alkoxycarbonyl group having 2 to 22 carbon atoms (such as a
methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group or
a dodecyloxycarbonyl group), an aryl group (which can be monocyclic or
bicyclic and may be unsubstituted or substituted, e.g., a phenyl group, a
p-sulfophenyl group, etc.), a heterocyclic ring residue (such as a
thiazole ring residue, an oxazole ring residue, an imidazole ring residue,
a thiadiazole ring residue, an oxadiazole ring residue, a triazole ring
residue, a tetrazole ring residue or a pyrimidine ring residue, the group:
##STR6##
being particularly advantageous), etc.
Specific examples of alkyl group represented by R.sup.4 are as follows: a
methyl group, an ethyl group, an n- or i-propyl group, an n-, sec, i- or
t-butyl group, an n-hexyl group, a dodecyl group, a heptadecyl group, a
chloromethyl group, a 2-chloroethyl group, a 2-cyanoethyl group, a
carboxymethyl group, a 2-carboxyethyl group, a 2-sulfoethyl group, a
3-sulfopropyl group, a 3-sulfobutyl group, a 4-sulfobutyl group, a
2-sulfatoethyl group, a 2-phosphoethyl group, a 2-hydroxyethyl group, a
3-hydroxypropyl group, a 2-methoxyethyl group, a 3-methoxypropyl group, a
2-ethoxyethyl group, a 2-(2-hydroxyethoxy)ethyl group, a
2-(2-acetoxyethoxy)ethyl group, a 2-(2-sulfoethoxy)ethyl group, a
2-[2-(3-sulfopropoxy)ethoxy]ethyl group, a 2-acetoxyethyl group, a
4-propionyloxybutyl group, an allyl group, a methoxycarbonylmethyl group,
a 2-(methoxycarbonyl)ethyl group, a 4-(ethoxycarbonyl)butyl group, a
butoxycarbonylmethyl group, a benzyl group, a 2-phenylethyl group, a
p-sulfobenzyl group and a 2-(2-mercapto-3-benzimidazolyl)ethyl group.
The alkyl groups represented by R.sup.5 and R.sup.6 respectively have 1 to
20 carbon atoms and include unsubstituted and substituted alkyl groups.
Examples of suitable substituents which the alkyl groups may have are a
halogen atom (such as a chlorine atom), a cyano group, a carboxy group, a
hydroxy group, an acyloxy group having 2 to 6 carbon atoms (such as an
acetoxy group), an alkoxycarbonyl group having 2 to 22 carbon atoms (such
as an ethoxycarbonyl group or a butoxycarbonyl group) and an aryl group
(which can be monocyclic or bicyclic and may be unsubstituted or
substituted, e.g., a phenyl group, a tolyl group, a p-sulfophenyl group,
etc.). Examples of advantageous alkyl groups are as follows: a methyl
group, an ethyl group, an n- or i-propyl group, an n-, i- or t-butyl
group, an amyl group (which may be straight or branched chain, hereinafter
the same), a hexyl group, an octyl group, a dodecyl group, a pentadecyl
group, a heptadecyl group, a chloromethyl group, a 2-chloroethyl group, a
2-cyanoethyl group, a carboxymethyl group, a 2-carboxyethyl group, a
2-hydroxyethyl group, a 2-acetoxyethyl group, an acetoxymethyl group, an
ethoxycarbonylmethyl group, a butoxycarbonylmethyl group, a
2-methoxycarbonylethyl group, a benzyl group, an o-nitrobenzyl group and a
p-sulfobenzyl group.
The aryl groups represented by R.sup.4, R.sup.5 and R.sup.6 respectively
can be monocyclic or bicyclic, preferably monocyclic, and include both
unsubstituted and substituted aryl groups. Examples of suitable
substituents for the aryl groups are an alkyl group having 1 to 20 carbon
atoms (such as a methyl group, an ethyl group or a nonyl group), an alkoxy
group having 1 to 20 carbon atoms (such as a methoxy group or an ethoxy
group), a hydroxy group, a halogen atom (such as a chlorine atom or a
bromine atom), a carboxy group and a sulfo group. Specific examples of
aryl groups are a phenyl group, a p-tolyl group, a p-methoxyphenyl group,
a p-hydroxyphenyl group, a p-chlorophenyl group, a 2,5-dichlorophenyl
group, a p-carboxyphenyl group, an o-carboxyphenyl group, a 4-sulfophenyl
group, a 2,4-disulfophenyl group, a 2,5-disulfophenyl group, a
3-sulfophenyl group and a 3,5-disulfophenyl group.
The alkoxycarbonyl groups represented by R.sup.5 and R.sup.6 respectively
have, preferably, 2 to 22 carbon atoms. Specific examples of suitable
alkoxycarbonyl groups include a methoxycarbonyl group, an ethoxycarbonyl
group, a butoxycarbonyl group, etc. The alkylthio groups represented by
R.sup.5 and R.sup.6 respectively have an alkyl moiety with 1 to 6 carbon
atoms, preferably 1 to 3 carbon atoms. Specific examples of suitable
alkylthio groups include a methylthio group, an ethylthio group, a
butylthio group, etc. The alkyl moiety of both the alkoxycarbonyl group
and the alkylthio group may be unsubstituted or substituted.
The 5- or 6-membered ring formed by R.sup.5 and R.sup.6 can be, e.g., a
carbocyclic ring such as a benzene ring, a cyclohexane ring, etc., or a
heterocyclic ring containing a hetero atom, e.g., a nitrogen atom, such as
a pyridine ring, a pyrimidine ring, a pyrrole ring, a pyrazole ring, an
imidazole ring, a triazole ring, etc. A pyrazole ring, an imidazole ring
and a triazole ring are preferred.
The alkylthiocarbonyl group represented by R.sup.3 has, preferably, 2 to 6
carbon atoms. Suitable examples of alkylthiocarbonyl groups for R.sup.3
are groups such as an ethylthiocarbonyl group, etc. Suitable examples of
alkoxycarbonyl groups for R.sup.3 include groups such as a methoxycarbonyl
group, an ethoxycarbonyl group, a butoxycarbonyl group, etc., suitable
examples of alkoxycarbonylmethyl groups for R.sup.3 include groups such as
an ethoxycarbonylmethyl group, etc., and suitable examples of
aryloxycarbonylmethyl groups for R.sup.3 include groups such as a
phenoxycarbonylmethyl group, etc. The alkyl moiety thereof may be
unsubstituted or substituted.
The bond between Y and Z in the general formulas set forth above is
presented schematically and may be single bond or double bond, depending
on what Y represents. More specifically, when Y represents a sulfur atom,
a selenium atom, an oxygen atom or an --NR.sup.4 -- group, the bond
between Y and Z is a single bond, and when Y represents a nitrogen atom,
the bond between Y and Z is a double bond.
Silver halide grains having an average grain size of not more than about
0.7.mu. which are present in the silver halide emulsion layer containing a
binder in an amount of not more than about 250 g per mol of silver halide
in this invention are substantially the surface latent image type. In
other words, they are not substantially the internal latent image type.
The expression "substantially surface latent image type" as used in this
specification means that the sensitivity obtained by (A) surface
development is higher than that obtained by (B) internal development when
development is carried out by (A) a surface development method and (B) an
internal development method described below after exposure to light for 1
to 1/100 second. The sensitivity as used herein is defined as follows:
S=100/Eh
wherein S is the sensitivity, and Eh is the exposure amount required to
obtain a density just intermediate between the maximum density (Dmax) and
the minimum density (Dmin), i.e., 1/2(Dmax+Dmin).
(A) Surface Development
Development is carried out at a temperature of 20.degree. C. for 10 minutes
in a developer of the following formulation.
N-Methyl-p-aminophenol (hemisulfate): 2.5 g
Ascorbic Acid: 10 g
Sodium Metaborate (tetrahydrate): 35 g
Potassium Bromide: 1 g
Water to make: 1 l
(B) Internal Development
After treatment at about 20.degree. C. for 10 minutes in a bleaching
solution containing 3 g/l of ferricyanide and 0.0125 g/l of phenosafranine
and then washing for 10 minutes, development is carried out at 20.degree.
C. for 10 minutes in a developer of the following formulation.
N-Methyl-p-aminophenol (hemisulfate): 2.5 g
Ascorbic Acid: 10 g
Sodium Metaborate (tetrahydrate): 35 g
Potassium Bromide: 1 g
Sodium Thiosulfate: 3 g
Water to make: 1 l
If the emulsion used in this invention is not substantially the surface
latent image type, a positive image is obtained in addition to a negative
image.
The average grain size of the silver halide grains that are substantially
the surface latent image type which are present in the silver halide
emulsion layer having a binder in an amount of not more than about 250 g
per mol of silver halide must not be more than about 0.7.mu.. The term
"average grain size" is commonly used by those skilled in the art of
silver halide photography and is well understood. The term "grain size"
means the diameter of the grains when the grains are spherical or
approximate spheres. With cubic grains, the grain size refers to the
length of an edge=.sqroot.4/.pi.. The average grain size is determined in
terms of the algebraic average or geometric average based on the projected
area of the grains. The details of the measurment of the average grain
size is described in C. E. K. Mees & T. H. James, The Theory of the
Photographic Process, 3rd Ed., pp. 36-43, Macmillan, New York (1966).
If the average grain size of the silver halide grains in the photographic
emulsion layer which the light-sensitive material of this invention
indispensably has exceeds about 0.7.mu., a very high contrast (e.g., more
than 8 as expressed by .gamma.) cannot be obtained using a stable
developer containing sulfite ions in a concentration of more than about
0.15 mol/l. The average grain size of the emulsion of this invention is
preferably not more than 0.4.mu.. Although the average grain size is
small, the light-sensitive material of this invention has high sensitivity
characteristics.
The silver halide present in the photographic emulsion which is used in
this invention may be any of silver chloride, silver bromide, silver
chlorobromide, silver iodobromide and silver iodochlorobromide. For silver
iodobromide or silver iodochlorobromide, the content of silver iodide is
preferably not more than about 10 mol%, and particularly preferably is 6
mol% or less. According to this invention, silver bromide, silver
iodobromide or silver chlorobromide (or silver iodochlorobromide)
containing a high percentage of silver bromide can also be used, and,
therefore, high sensitivity can more easily be obtained as compared with
the method in which a conventional lith-type ultra-contrasty
light-sensitive material is used. Where silver chloride is used, the
content of silver chloride is preferably not more than about 80 mol% of
the total silver halide and, particularly preferably is not more than 50
mol%.
The photographic emulsion layers which have an average grain size of not
more than about 0.7.mu. and are substantially the surface latent image
type, of which, at least one, is present in the light-sensitive material
of this invention, must not contain a binder in an amount of more than
about 250 g per mol of silver halide. A suitable amount of the binder can
range from about 20 g to about 250 g per mol of silver halide. If the
binder content is more than about 250 g per mol of silver halide, it is
impossible to provide contrasty photographic chracteristics, and
particularly, to provide extremely contrasty photographic characteristics
which is an object of this invention.
The general tendency of photographic emulsions is that the smaller is the
amount of a binder present in the emulsion, the higher is the contrast
which is obtained. This effect is due to an increase in the amount of
silver halide present in the emulsion layer of a unit thickness. The
influence of the silver halide content in this invention differs from such
known effect, and the effect on the image remarkably changes in the
vicinity of the above-described upper limit. The effect of this invention
can be produced only when the average grain size is not more than about
0.7.mu. and the emulsion contains a high percentage of silver halide, as
described above.
Gelatin is advantageously used as a binder or protective colloid in the
photographic emulsion, but other hydrophilic colloids can also be used.
For example, gelatin derivatives, graft polymers of gelatin with other
high molecular weight materials, proteins such as albumin or casein,
cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl
cellulose or cellulose sulfate, saccharide derivatives such as sodium
alginate or starch derivatives, various synthetic hydrophilic high
molceular weight materials such as homopolymers or copolymers, e.g.,
polyvinyl alcohol, polyvinyl alcohol (partial acetal), poly-N-vinyl
pyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide,
polyvinyl imidazole, polyvinyl pyrazole, etc., can be used.
Lime-processed gelatin and acid-processed gelatin can be used as the
gelatin. Also, gelatin which is hydrolyzed or decomposed by enzymes can be
used. Suitable gelatin derivatives are those which are prepared by
reacting gelatin with various compounds such as acid halides, acid
anhydrides, isocyanates, bromoacetic acid, alkanesultones,
vinylsulfonamides, maleinimide compounds, polyalkylene oxides or epoxy
compounds. Specific examples of these gelatin derivatives are described
in, e.g., U.S. Pat. Nos. 2,614,928, 3,132,945, 3,186,846 and 3,312,553,
British Pat. Nos. 861,414, 1,033,189 and 1,005,784, Japanese Patent
Publication No. 26,845/67, etc.
Examples of gelatin graft polymers include those prepared by grafting a
homopolymer or a copolymer of a vinylic monomer such as acrylic acid,
methacrylic acid, the derivatives thereof (such as the esters or the
amides thereof), acrylonitrile or styrene to gelatin. In particular, graft
polymers prepared from polymers which are compatible with gelatin to some
degree, such as those of acrylic acid, methacrylic acid, acrylamide,
methacrylamide or hydroxyalkyl methacrylate are preferred. Examples of
these polymers are described in, e.g., U.S. Pat. Nos. 2,763,625, 2,831,767
and 2,956,884, etc. Typical synthetic hydrophilic high molecular weight
materials are described in, e.g., German Patent Application (OLS) No.
2,312,708, U.S. Pat. Nos. 3,620,751 and 3,879,205, Japanese Patent
Publication No. 7,561/68, etc.
The photographic light-sensitive material of this invention must conain at
least one of the photographic emulsion layers having the above-described
characteristics, but if desired, one or more other types of silver halide
photographic emulsion layers can be present. As to the latter emulsion
layers, the average grain size of the silver halide may be more than about
0.7.mu. and also a binder may be present in an amount of more than about
250 g per mol of silver halide. Moreover, the emulsion layers may have
been chemically sensitized using known techniques. The mutual relationship
of the arrangement between the photographic emulsion layer which meets the
requirements of this invention and the other emulsion layers is not
particularly restricted, and either of them may be positioned nearer the
support. However, in order to satisfactorily produce the effect of this
invention, it is preferred for all of the photographic emulsion layers to
be silver halide emuslions of the negative image type, i.e., negative
image silver halide emulsions which satisfy the requirements of this
invention as to the average grain size, the binder content and the
distribution of the latent image.
Although the silver halide emulsions used in the present invention need not
necessarily be chemically sensitized, chemically sensitized silver halide
emulsions are preferred. Processes for chemical sensitization of the
silver halide emulsions which can be used include known sulfur
sensitization, reduction sensitization and noble metal sensitization
processes. These processes are described in references such as P.
Glafkides, Chimie et Phisique Photographique, Paul Montel, Paris (1967) or
Zelikmann, Making and Coating Photographic Emulsions, The Focal Press,
London (1964) or H. Frieser, Die Grundlagen der photographischen Prozesse
mit Silberhalogeniden, Akademische Verlagsgesellschaft (1968). In the
noble metal sensitization processes, a gold sensitization process is a
typical process where gold compounds or mainly gold complexes are used.
However, if the gold sensitizing agents are used in an amount effective to
carry out chemical sensitization, a softening of the tone occurs.
Accordingly, gold sensitization is not as suitable for the present
invention. No difficulties occur using complexes of noble metals other
than gold, such as those of platinum, palladium or iridium, etc. A
reduction sensitization process may be used if the process does not
generate a fog which causes practical difficulties. However, reduction
sensitization is not as preferred because control of the process
conditions is difficult. A preferred chemical sensitization process for
the present invention is the use of a sulfur sensitization process. In the
present invention, it is preferred for the silver halide emulsions
substantially not to be subjected to gold sensitization and it is
particularly preferred for the silver halide emulsions to be chemically
sensitized using only a sulfur sensitization process.
Examples of sulfur sensitizing agents which can be used include not only
sulfur compounds present in the gelatin per se but also various sulfur
compounds such as thiosulfates, thioureas, thiazoles or rhodanines, etc.
Examples of suitable sulfur compounds are described in U.S. Pat. Nos.
1,574,944, 2,410,689, 2,278,947, 2,728,668 and 3,656,955. Typical examples
of reduction sensitizing agents which can be used include stannous salts,
amines, formamidine sulfinic acid and silane compounds, etc., as described
in U.S. Pat. Nos. 2,487,850, 2,518,698, 2,983,609, 2,983,610 and
2,694,637. Complex salts of Group VIII metals in the Periodic Table, such
as platinum, iridium or palladium, etc., can be used for noble metal
sensitization and examples thereof are described in U.S. Patent 2,448,060
and British Patent 618,061, etc.
Of the compounds represented by the above-described general formula (I),
preferred are compounds represented by the following general formula (Ia):
R.sup.1 NHNHCHO (Ia)
In the above formula, R.sup.1 has the same meanings as in the
above-described general formula (I).
Of the compounds of the above general formula (Ia), compounds represented
by the following general formula (Ib) are preferred.
R.sup.11 NHNHCHO (Ib)
In the above formula, R.sup.11 represents an unsubstituted phenyl group or
a tolyl group.
Specific examples of the compounds represented by the general formula (I)
are given below, but this invention is not to be construed as being
limited thereto.
##STR7##
The compounds represented by the general formula (I) can be synthesized by
reacting hydrazines with formic acid or by reacting hydrazines with acyl
halides. Starting material hydrazines such as
##STR8##
are commercially available and hydrazines of the formula
##STR9##
where R represents an alkyl group can be synthesized by reduction of a
p-nitrophenylhydrazine. Suitable acyl halides which can be used include
aliphatic acyl halides such as acetyl chloride, propionyl chloride,
butyryl chloride, etc., and aromatic acyl halides such as benzoyl
chloride, toluoyl chloride, etc. The reaction can be conducted in a
solvent such as benzene, chloroform, pyridine, triethylamine, etc., and at
a temperature of about 0.degree. C. to about 100.degree. C., preferably
0.degree. C. to 70.degree. C. A suitable molar ratio of the hydrazine to
the acyl halide in the presence of a base such as pyridine or
triethylamine which acts as a hydrogen halide acceptor for the hydrogen
halide formed as a by-product ranges from about 1:1 to about 1:3,
preferably 1:1.2 to 1:1.5 and in the absence of such a base ranges from
about 1:0.3 to about 1:1, preferably 1:0.45 to 1:0.5. Hydrogen halide
accepting agents such as triethylamine and pyridine can be employed in an
amount of about 1 mol or more per mol of the acyl halide used.
Specific examples of the synthesis of the compounds of the general formula
(I) are set forth below. Unless otherwise indicated herein, all parts,
percents, ratios and the like are by weight.
Synthesis Example I
(Synthesis of Compound (I-2))
110 l g of formic acid was stirred at 25.degree. to 30.degree. C., and to
this, 107 g of p-tolylhydrazine was gradually added. After completing the
addition, heating was performed at 50.degree. C. for 20 minutes while
stirring the mixture. After cooling the mixture with ice, the resulting
crystals were filtered out and recrystallized from 550 ml of acetonitrile
to obtain 54.5 g of colorless needles having a melting point of
176.degree. to 177.degree. C.
Synthesis Example II
(Synthesis of Compound (I-5))
15 g of p-tolylhydrazine was added to 100 ml of acetonitrile at 25.degree.
to 30.degree. C. while stirring. Then, 15 g of benzoyl chloride was added
dropwise at 25.degree. to 30.degree. C. After completing the addition,
stirring was continued at 25.degree. to 30.degree. C. for 6 hours. After
c | | |
