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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sensitized silver halide photographic material.
More particularly, this invention relates to a silver halide photographic
material containing sensitized fine silver halide crystals.
2. Description of the Prior Art
A photographic material containing fine silver halide particles, for
example, those having an average diameter of 0.1 micron, is useful for
recording minute images since images having a very small granularity and a
superior sharpness can be obtained. However, the sensitivity of such a
photographic material is generally lower than that of a photographic
material containing relatively larger silver halide particles, for
example, those having an average diameter of 0.6 micron, because the
sensitivity of a silver halide photographic material generally tends to
increase with larger sizes of silver halide particles. In general,
therefore, the use of a photographic material containing fine silver
halide particles requires large quantities of exposue and thus, a light
source of a large luminous intensity or long exposure time, and this has
set great limitation on the use of photographic materials containing fine
silver halide particles. It is of great importance to increase the
sensitivity of photographic materials containing fine silver halide
particles to a level which is feasible for practical purposes.
Many methods have previously been known for increasing the sensitivity of a
silver halide photographic material without increasing the particle size
of the silver halide.
Among these are a method in which a sulfur compound such as sodium
thiosulfate, a noble metal compound such as gold chloride, or other
reducing agent such as tin chloride is added during the process of
chemical ripening of a silver halide photographic emulsion, and a method
in which immediately prior to coating, a quaternary ammonium salt-type
compound, such as an alkyl pyridinium chloride or a polyoxyalkylene
compound is added to a photographic emulsion.
These known sensitizing methods, however, cannot effect a sufficient
elevation of the sensitivity without adversely affecting the photographic
material containing the fine silver halide particles. Even when great
sensitizing effects are obtained using these methods, a decrease in
radient or fog may occur during storage of the photographic material.
A primary object of this invention is to provide a silver halide
photographic material containing very fine silver halide particles in the
photographic layer and having a high sensitivity.
A further object of this invention is to provide a photographic material
containing fine silver halide particles which has a high sensitivity and a
high gradient.
Another object of this invention is to provide a photographic material
containing fine silver halide particles which has a high sensitivity and
is free from fog during storage.
SUMMARY OF THE INVENTION
The sensitivity of a photographic material containing fine silver halide
particles can be markedly increased by incorporating a heterocyclic
compound containing a hydroxylamino substituent into a photographic layer
containing fine silver halide particles with an average particle diameter
not in excess of 0.35 micron or containing fine silver halide particles at
least 90% of which have a particle diameter not in excess of 0.4 micron.
It has been found that such a photographic layer does not have a decrease
in gradient with increasing sensitivity, nor does fog occur during
storage.
This invention is achieved by adding an appropriate amount of a
nitrogen-containing heterocyclic compound having a hydroxylamino group as
a substituent to a photographic emulsion of fine silver halide particles,
preferably, which have already been sensitized or to a hydrophilic
substance layer adjoining the silver halide emulsion layer directly or via
some other hydrophilic substance layer.
DETAILED DESCRIPTION OF THE INVENTION
As the compound to be incorporated in the photographic emulsion,
heterocyclic compounds of the following general formula are especially
effective:
##EQU1##
wherein Z represents an atomic grouping necessary for forming a
heterocyclic ring with the
##EQU2##
moiety of said formula and contains at least one nitrogen atom and X
represents a nitrogen atom or a methine group (--CH=).
There are various nitrogen-containing hetero rings formed by the Z atomic
grouping. But compounds containing a triazine ring, a triazine ring which
is a part of a fused ring system (e.g.) a benzene ring as a part of a
fused ring system, a pyrimidine ring, or a pyrimidine ring which is a part
of a fused ring system (e.g.) a triazole ring or pyrazole ring as a part
of a fused ring system are easy to synthesize and exhibit superior
effects.
That is, heterocyclic compounds of the following general formula
(II.sub.a), (II.sub.b), (III.sub.a), (III.sub.b), or (III.sub.c) are
especially effective:
Triazine Type
##EQU3##
wherein R.sub.1 and R.sub.2 each represents a hydrogen atom, a hydroxy
group, a halogen atom (e.g. a chlorine atom, a bromine atom), an alkyl
group (e.g. a methyl group, an ethyl group, a propyl group, a butyl group,
etc.), an alkoxy group (e.g. a methoxy group, an ethoxy group, etc.), an
aryl group (e.g. a phenyl group), or an optionally substituted amino group
{e.g. an amino group, a hydroxyamino group, an alkylamino group (e.g. a
methylamino group, an ethylamino group), a di-alkylamino group (e.g. a
di-methylamino group, a di-ethylamino group), an arylamino group (e.g. a
phenylamino group)}.
##EQU4##
wherein Y represents a benzene ring.
Pyrimidine Type
##EQU5##
wherein R.sub.3 and R.sub.4 each represents a hydrogen atom, a hydroxy
group, an alkyl group (e.g. a methyl group, an ethyl group, a propyl
group, a butyl group), an alkoxy group (e.g. a methoxy group, an ethoxy
group), an aryl group (e.g. a phenyl group), or an optionally substituted
amino group {e.g. an amino group, an alkylamino group (e.g. a methylamino
group, an ethylamino group), a hydroxyamino group}.
##EQU6##
wherein R.sub.5 has the same meaning as R.sub.3 and R.sub.4, and R.sub.6
represents a hydrogen atom, an alkyl group (e.g. a methyl group, an ethyl
group), an aralkyl group, or an aryl group (e.g. a phenyl group).
##EQU7##
wherein R.sub.7 has the same meaning as R.sub.3 and R.sub.4, R.sub.8 has
the same meaning as R.sub.6 and R.sub.9 represents a hydrogen atom, an
optionally substituted alkyl group {e.g. a methyl group, an ethyl group,
an alkoxyalkyl group (e.g. a methoxyethyl group), an aralkyl group (e.g. a
phenylethyl group)}, or a hydroxy group.
Specific examples of the nitrogen-containing heterocyclic compound
containing a hydroxylamino group which can be used in the present
invention are shown below. These compounds can be used alone or in
admixture. It should be understood that the compounds which can be used in
this invention are not limited in any way to these specific examples.
##EQU8##
These compounds can be prepared by reacting chloro-S-triazine or its
substitution products with the corresponding amines, phenols or alcohols.
These compounds have been synthesized in accordance with the methods
disclosed in the Journal of the American Chemical Society, Vol. 73, page
2981 and the Journal of the Organic Chemistry, Vol. 27, page 4054.
Typical examples of synthesis will be given below.
EXAMPLE OF SYNTHESIS (COMPOUND 1)
cyanuric trichloride (92.2 g) was dissolved in 200 ml. of dioxane. With
good stirring, the solution was poured into 300 ml. of water to make a
slurry. The resultant slurry was cooled to 0.degree. - 5.degree.C., and
64.4 g of an aqueous solution of ethylamine (70% by weight) was added
dropwise. The mixture was heated to 40.degree.C., and the pH of the
reaction mixture was maintained neutral by the addition of 30 ml. of an
aqueous solution containing 40 g of sodium hydroxide. After a lapse of 4
hours, the precipitated crystals were recovered by filtration, and washed
with water. Hydroxylamine hydrochloride (140 g) was dissolved in 300 ml.
of water, and the solution was cooled to 20.degree.C. or below, after
which 170 ml. of an aqueous solution containing 80 g of sodium hydroxide
was added, under a nitrogen atomosphere, so as to neutralize the solution.
To the neutralized solution was added a suspension of the initially
synthesized crystals in 500 ml. of dioxane, and the mixture was reacted
for 30 minutes at 50.degree.C. and further for 4 hours at 85.degree.C. The
insoluble matter was separated by filtration, and when the filtrate was
cooled, crystals were precipitated. The crystals were recovered by
filtration, and recrystallized from methanol. Crystals having a melting
point of 197.degree. to 198.degree.C were obtained.
Compounds 2 to 4 and 7 to 9 were synthesized using the corresponding amines
in accordance with substantially the same method as in the preparation of
Compound 1.
Compound 5 can be synthesized in a similar manner using
2-phenyl-4,6-dichloro-1,3,5-triazine prepared by the method described in
the Journal of the American Chemical Society, Vol. 60, page 1657. Compound
6 can also be synthesized using a 2-ethyl derivative. Compounds 12 to 21
can be produced by methods similar to the above by the reaction of the
chlorine-substituted products of the corresponding heterocyclic compounds
with hydroxylamine.
These compounds can be added to a photographic emulsion as a solution of an
organic solvent, for example, alcohols such as methanol, ethanol,
propanol, iso-propanol, ketones such as acetone, methyl ethyl ketone and
esters such as ethyl acetate or as an aqueous solution weakly acidified
with an acid such as hydrochloric acid, sulfuric acid and p-toluene
sulfonic acid.
Although there is no specific restriction on the point at which this
compound is added to an emulsion, it is convenient to add it immediately
before coating which follows post ripening.
It is necessary that the silver halide emulsion have an average particle
diameter of not more than 0.35 micron, or at least 90% of the total
particles should have a particle diameter not in excess of 0.4 micron. In
the following description, the emulsion containing fine particles of
silver halide means such a photographic emulsion. The particle sizes of
the spherical grains are determined by a diameter while those of the other
shapes can be determined by a diameter of the equivalent circle to a
projected area (See "Empirical Relations Between Sensitometric And
Size-frequency Characteristics In Photographic Emulsion Series" by A. P.
H. Trivelli and W. F. Smith in The Photographic Journal, Vol. LXXIX,
pp330--338, 1939 ). The average particle diameter of the grains can be
determined by any one of several kinds of the measurement such as
arithmetric average and geometric average. The above-described methods of
determining grain size for the present invention are not critical,
regardless of the means employed, providing that the particle sizes have
the above-defined values.
The effect produced by the above-described compound is barely obtained with
a photographic layer having relatively larger silver halide particles (for
example, those with a diameter of 0.6 micron) as used in a conventional
negative photographic material. In view of this, it is clear that the
sensitizing method used in this invention differs from the known
sensitizing methods described above.
The silver halide photographic emulsion used in this invention can be one
which has been sensitized in advance using a chemical sensitizing method
such as noble metal sensitization (as described in U.S. Pat. No.
2,399,083) reduction sensitization (as described in U.S. Pat. Nos.
2,518,698, 2,419,974, and 2,983,610) or sulfur sensitization (as described
in U.S. Pat. No. 2,410,689). In such a case, a higher sensitivity can be
obtained by the conjoint use of the sensitizing method of this invention
and such a conventional sensitizing method. When a spectral sensitizing
dye is conjointly used with the heterocyclic compound described above, the
sensitivity of the photographic material in a spectral sensitization
spectral region can be increased to an even greater degree than in the
case of using a spectral sensitizing dye alone.
Furthermore, it has been found that a synergistic sensitizing effect is
obtained when the sensitization method of this invention is employed
together with a spectral sensitizing organic compound having a large
sensitizing effect on a silver halide emulsion of ultrafine particles (as
described in the specification of U.S. Ser. No. 38,485, filed May 18, 1970
and Ser. No. 13,774, filed Feb. 24, 1970).
The composition of the silver halide used is not particularly restricted,
and any of silver bromide, silver chloride, silver iodide, silver
iodobromide, silver chlorobromide, silver iodochloride, and silver
iodochlorobromide can be used. Silver bromide and silver iodobromide are
preferred on account of a high sensitivity. The weight ratio of the
hydrophilic binder to the silver halide can range from 4/1 to 1/5,
preferably from 2/1 to 1/3.
The amount of the hydroxylamine group containing compound can vary over a
broad range, but a preferred range is from about 10mg to about 10g,
especially about 40 mg to about 3 g, per mole of silver. A suitable
emulsion coating amount on a support can range from about 20 g to about
500 g per m.sup.2 of the support.
A hydrophilic high-molecular-weight substance which is used as a binder
medium in the emulsion layer in the practice of this invention is suitably
gelatin (i.e., an acid-processed or a lime-processed gelatin used in a
conventional photographic material) or other modified gelatins (gelatin
derivatives) such as acetylated gelatin or phthalized gelatin. It is also
possible to use synthetic polymeric materials such a polyvinyl alcohol,
polyacrylic acid, polyacrylamide, or copolymers thereof such as
acrylamide-1-vinyl-2-methylimidazole, as
acrylamide-1-vinyl-2-methylimidazole acrylic acid and the like. Examples
of the hydrophilic high-molecular weight substances are disclosed in U.S
Pat. Nos. 3,167,430 and 3,284,207 and also disclosed in U.S. Pat. Nos.
2,461,023, 2,486,190 and 2,811,494, British Pat. No. 646,712 and S.C.I.
Ind. Phot; Vol. 24, p. 344,1953.
During the manufacture of the photographic material of this invention,
natural surface active agents such as saponin or synthetic surface active
agents such as alkylbenzenesulfonic acids or polyoxyalkylene alkyl phenols
can be used (See, for example, U.S. Pat. Nos. 3,415,649 and 3,201,252).
Known hardening agents such as glyoxal, dimethylol urea, mucochloric acid,
tri(ethyleneimino)-S-triazine or dichlorohydroxy-S-triazine can also be
used (See, for example, U.S. Pat. Nos. 2,983,619 and 3,325,287). Known
stabilizers (See e.g., U.S. Pat. Nos. 2,450,397 and 2,319,090) or
antifoggants (See, e.g., U.S. Pat. Nos. 2,403,927 and 2,465,149) can also
be incorporated in the emulsion layer in order to prevent changes in the
properties or fog on storage. This does not affect the effects obtained by
the invention, and photographic materials of desirable properties can be
obtained.
The emulsion layer of the photographic material of this invention can also
contain various additives such as a toner, an agent for preventing latent
image fading, a softener for the emulsion layer (See U.S. Pat. Nos.
2,860,980 and 2,904,434), an anti-curling agent (See, e.g., U.S. Pat. No.
3,547,642), a lubricant, a matting agent, a development accelerator (See,
e.g., U.S. Pat. Nos. 2,423,549 and 2,400,532) or an irradiation-preventing
dye (See, e.g., U.S. Pat. Nos. 3,483,632 and 2,865,752).
Furthermore, the photographic emulsion layer of fine particles of silver
halide can contain color couplers which are used in color photograhic
materials. The color couplers can be water-soluble couplers or they can be
insoluble and can be added to the emulsion layer as a dispersion (See, for
example, U.S. Pat. Nos. 3,409,439, 3,551,155 and 3,551,156 as yellow
couplers, U.S. Pat. No. 3,558,319 as magenta couplers and U.S. Pat. No.
3,591,393 as cyan couplers)
The support material of the photographic material of this invention is not
restricted in any way. Good effects are obtained by coating such emulsion
layer on any support materials such as polyester films, cellulose
triacetate films or other film bases, paper bases such as baryta paper,
resin-coated paper or synthetic paper, dry glass plate, or metal plates.
The sensitivity of a photographic material having fine silver halide
particles can be increased not only by adding the heterocyclic compound
described above to a photographic emulsion containing fine particles of
silver halide, but also by immersing a support material coated with the
emulsion layer and dried, in a solution containing the heterocyclic
compound. In the latter case, the compound having the sensitizing ability
diffuses into the emulsion layer from the solution in which the
photographic material is immersed, and thus gives the same effect as in
the case of adding the compound to the emulsion prior to coating.
Furthermore, the same effect as in the present invention is obtained by
incorporating the heterocyclic compound described above in a hydrophilic
substance layer adjoining the silver halide emulsion layer directly or via
some other hydrophilic substance layer.
In this case, the heterocyclic compound added to the hydrophilic substance
layer diffuses towards the silver halide emulsion layer while these layers
are in the wet condition as a result of coating these layers
simultaneously or sequentially, and thus, the same result is produced as
if the compound had been added to the silver halide emulsion layer
initially.
The present invention will be illustrated in greater detail by reference to
the following Examples which are for the purposes of illustration and are
in no way intended to limit the scope of the invention.
EXAMPLE 1
A photographic emulsion of gelatin/silver iodobromide having an average
particle diameter of 0.06 micron was prepared. This emulsion contained
60.5 g of silver bromide, 0.7 g of silver iodide and 56 g of gelatin per
kilogram of emulsion. In the course of preparation,
N,N,N'-triethylthiourea was added to the emulsion after removal of the
water-soluble salts, and the emulsion was chemically ripened for 80
minutes at 54.degree.C. After chemical ripening, 9 kg of the emulsion was
divided into 9 equal portions each weighing 1 kilogram. These portions
were designated as A,B,C,D,E,F,G,H and J. Compounds 1, 2, 3, 4, 11, 12, 14
and 15 were added, respectively, to portions B to J in the amounts as
indicated in Table 1 below. Each of these compounds was added as a 0.8% or
0.02% by weight methanol solution.
Table 1
______________________________________
Solution
Emulsion
Compound Amounts of Concentration
Sample Added Compound Added
(wt %)
______________________________________
A None -- 0.8
B 1 0.95 g 0.8
C 2 0.8 g 0.8
D 3 0.7 g 0.8
E 4 1.6 g 0.8
F 11 1.3 g 0.8
G 12 0.35 g 0.8
H 14 20 mg 0.02
J 15 30 mg 0.02
______________________________________
Each of the emulsions A to J was coated on a glass support at a rate of 350
cc/m.sup.2, and dried. The sensitivity of the dried samples to light from
a tungsten-filament lamp was measured. Each of the dried samples was
exposed for 10 seconds using an optical wedge, and developed for 5 minutes
at 20.degree.C. using a developer solution of the following formulation.
______________________________________
Composition of the Developer
N-Methyl-para-Aminophenol Sulfate
2 g
Sodium Sulfite 96 g
Hydroquinone 8.8 g
Sodium Carbonate Monohydrate
56 g
Potassium Bromide 5 g
Water to make 1000 cc
______________________________________
The results obtained in measuring the sensitivity are shown in Table 2. The
sensitivity value is the reciprocal of the amount of exposure which will
give a photographic density of 1 above a fog value. The values shown in
Table 2 are relative values with the sensitivity of Sample A set at 1.
Table 2
______________________________________
Emulsion Sample Relative Sensitivity
______________________________________
A 1.0
B 7.6
C 1.35
D 4.9
E 8.6
F 1.25
G 1.8
H 4.4
J 2.9
______________________________________
As can be seen from the above results, the sensitivity of the photographic
material containing ultrafine silver halide particles was markedly
increased by the addition of Compound 1,3,4,12,14,or 15. Furthermore, the
sensitivity evidently increased due to the addition of Compound 2 or 11.
The emulsions tested had the same spectral sensitivity characteristics.
EXAMPLE 2
Using the same photographic emulsion of ultrafine silver iodobromide
particles as was used in Example 1, after chemical ripening 6 kg of the
emulsion were divided into six portions each weighing 1 kg. To these
portions were added a sensitizing dye,
3-allyl-5-[1-(2-carboxyphenyl)-2-(3-ethyl-2-thiazolinylidene)ethylidene]
rhodanine, and Compounds 1, 2, 3, 4, and 12 as indicated in Table 3 below.
Table 3
______________________________________
Emulsion
Sensitizing Sensitizing Compounds
Sample Dye Compound No. Amounts
(g) (g)
______________________________________
a 0.12 None --
b " 1 0.95
c " 2 0.8
d " 3 1.1
e " 4 1.6
f " 12 0.35
______________________________________
Each of these emulsion samples was coated on a glass support in the same
manner as shown in Example 1 to form a dry plate. The photographic
sensitivities of these dry plate samples to green and blue lights were
measured. As a light source, a tungsten-filament incandescent lamp was
used, and the measurement of the sensitivity to a blue light or green
light was performed by exposing each of the samples through a blue filter
having a maximum percent transmission at a wavelength of 434 nm or a green
filter having a maximum percent transmission at a wavelength of 535 nm.
The former gives the sensitivity in an inherent sensitivity wavelength
region of the photographic silver halide emulsion layer, and the latter
gives the sensitivity in a spectral sensitization wavelength region of the
silve halide emulsion layer. Each of the photographic materials was
developed in the same manner as described in Example 1, and the
sensitivity of the photographic material was measured. The results
obtained are shown in Table 4. The sensitivity value is the reciprocal of
the amount of exposure required to give a photographic density of 0.1
above a fog value. The sensitivity of the sample a to blue light or green
light is set at 1, and the relative sensitivity values of the other
samples are given in the table.
Table 4
______________________________________
Sample Relative Sensitivity
To Blue Light
To Green Light
______________________________________
a 1.00 1.00
b 1.38 1.26
c 1.70 1.74
d 1.86 1.86
e 1.58 1.55
f 1.62 1.41
______________________________________
By the addition of any of the Compounds 1,2,3,4, and 12, an extreme
increase in the sensitivity of the photographic emulsion containing
ultrafine silver halide grains was obtained.
EXAMPLE 3
A silver bromide emulsion having an average particle diameter of 0.10
micron was prepared.
One kilogram of this emulsion contained 85 g of silver bromide and 42 g of
gelatin. Four kilograms of the emulsion were divided into four portions
each weighing 1 kg. Compounds 1, 2 and 3 were added respectively to these
portions as shown in Table 5 below, and each of the emulsions was coated
on a cellulose triacetate base and dried. The thickness of the coating
after drying was 10 microns.
Table 5
______________________________________
Sample Compounds Added Amount
(g)
______________________________________
K None --
L (Compound 1)
2-Hydroxylamino-4,6-di-
(ethylamino)-1,3,5-triazine
0.65
M (Compound 2)
2-Hydroxylamino-4,6-di(di-
ethylamino)-1,3,5-triazine
1.6
N (Compound 3)
2,4-Di(hydroxylamino)-6-
diethylamino-1,3,5-triazine
1.45
______________________________________
The sensitivity of each of the films coated with the emulsions K to N to a
tungsten-filament electric lamp was measured. The measurement method and
the method of expression were the same as were used in Example 1. The
results obtained are shown in Table 6 below.
Table 6
______________________________________
Relative
Samples No. Sensitivity Fog
______________________________________
K 1.0 0.04
L 4.3 0.04
M 1.2 0.05
N 4.0 0.04
______________________________________
The sensitivity of the emulsion layers containing Compounds 1 and 3 was
elevated to a great degree. With compound 2 also, the sensitivity
evidently increased.
EXAMPLE 4
Three silver iodobromide emulsions P, Q and R having an average particle
diameter of 0.2 micron, 0.33 and 0.5 micron, respectively, were prepared.
One kilogram of each of these emulsion contained 55 g of the silver halide
and 28 g of gelatin. The silver halide contained 0.6 mol% of silver
iodide.
These emulsions were all chemically sensitized with sodium thiosulfate and
chloroauric acid in a chemical ripening step. To 1 kg of each of the
emulsions was added 0.95 g of
2-hydroxylamino-4,6-di(ethylamino)-1,3,5-triazine (Compound 1 illustrated
above) as a 1% methanol solution. An emulsion sample which did not contain
this sensitizing compound was also prepared for the purposes of
comparison. Each of these emulsions was coated on a glass support, and the
sensitivity of the photographic material obtained was measured. The method
of measuring the sensitivity and the method of expressing the results were
the same as were used in Example 3. The results obtained are shown in
Table 7.
Table 7
______________________________________
Emulsion Average Par-
Addition of Relative
Sample ticle Diameter
Compound 1 Sensitivity
(microns)
______________________________________
P-1 0.2 no 1.00
P-2 0.2 yes 1.75
Q-1 0.33 no 1.00
Q-2 0.33 yes 1.28
R-1 0.5 no 1.00
R-2 0.5 yes 0.98
______________________________________
The sensitivities of the Samples P-2, Q-2 and R-2 were those relative to
the sensitivities of the Samples P-1, Q-1 and R-1 which are set at 1.00.
The sensitizing effect of Compound 1 on Emulsion P having an average
diameter of 0.2 micron was very great. But with increasing average
particle diameter, its sensitizing effects became smaller, and the
Compound 1 exhibited no sinsitizing effect on the emulsion containing
particles with an average particle size of 0.5 micron.
EXAMPLE 5
Two silver iodobromide emulsions containing 1 mole% of silver iodide and
having an average particle diameter of 0.06 micron were prepared. One of
them was a sulfur sensitized emulsion chemically sensitized with
N,N,N'-triethylthiourea, which was the same as that used in Examples 1 and
2. This emulsion was designated as S. The other emulsion was an emulsion
sensitized with N,N,N'-triethylthiourea and chloroauric acid. This
emulsion was designated as T.
The sensitizing dye and the sensitizing compound of this invention were
added to these two emulsions as shown in Table 8.
Table 8
______________________________________
Emulsion (i) (ii) (iii)
S S T
(1 kg) (1 kg) (1 kg)
______________________________________
Sensitizing Dye
3-Allyl-5-[1-(2-carboxy-
phenyl)-2-(3-ethyl-2-
100 mg 100 mg 100 mg
thiazolinylidene)ethyli-
dene] rhodanine
Sensitizing Compound 3
2,4-Di(hydroxylamino)-6-
-- 250 mg --
diethylamino-1,3,5-triazine
Emulsion Designation
after Addition of the
above Compounds U V W
______________________________________
After the addition of these compounds, each of the Emulsions U, V and W was
coated on a glass support and dried. The dry thickness of the coating was
5 microns. The resulting photographic material was subjected to
sensitometric testing. The photographic material was exposed for one
second to a tungsten-filament electric lamp through an optical wedge, and
then developed with a developer solution having the same composition as
that used in Example 1. The results of the test obtained are shown in
Table 9.
Table 9
______________________________________
Sample
U V W
______________________________________
Sensitivity
1.0 1.8 1.8
G (average
4.4 5.3 3.4
gradient)
Fog 0.02 0.02 0.03
______________________________________
The sensitivity shown in the above table was obtained by calculating the
reciprocal of the amount of exposure required to obtain a photographic
density of 2.0 above a fog value. The sensitivities of the Samples V and W
are relative sensitivities with the sensitivity of Sample U being set at
1.0.
The average gradient G is the gradient of a straight line connecting two
points which correspond to a photographic density of 0.1 and 2.0 (after
subtraction of fog) on the characteristic curve.
The sensitivity of the Emulsion W which was chemically sensitized by the
addition of the gold salt during chemical ripening increased to nearly two
times that of the Emulsion U which was only sulfur sensitized and
spectrally sensitized, but the average gradient of the Emulsion W was
lower. The Emulsion V which was sensitized chemically with Compound 3
instead of the gold salt increased in sensitivity to the same degree as
the Emulsion W, but had a higher average gradient. In the preproduction of
fine line images, the use of Emulsion W does not lead to a sharp
reproduction of the edges of the line image, but the use of the Emulsion V
gives very sharp edges to the reproduced line image.
EXAMPLE 6
A fine silver iodobromide emulsion containing 2 mol% of silver iodide and
having an average particle diameter of 0.10 micron was prepared.
Three kilograms of this emulsion were divided into three portions each
weighing 1 kg, which were designated as Emulsions X, Y and Z. The
compounds shown in Table 10 were added to Emulsions Y and Z.
Table 10
______________________________________
Sample Additive Amount
(mg)
______________________________________
X None --
Y Triethylene Tetramine
16
Z Compound 15 illustrated
above 15
______________________________________
Each of the emulsions was coated on a 0.13 mm thick cellulose triacetate
film at a rate of 80 g/100 cm.sup.2, and dried.
A portion of the film sample was allowed to stand for 7 days in an
atmosphere at 40.degree.C. and an RH of 80%. The films so treated and
those which had not been treated at 40.degree.C. were tested as to their
sensitivity to a tungsten-filament electric lamp. A developer solution
having the same composition as the developer solution used in Example 1
was used for the measurement of the sensitivity. The results obtained are
shown in Table 11.
Table 11
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Sample Treated at 40.degree.C:
Not Treated
Sensitivity Fog Sensitivity Fog
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X 1.0 0.07 1.0 0.03
Y -- 1.10 2.5 0.05
Z 2.2 0.07 2.2 0.03
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Due to the addition of the tetraethylene tetramine, the emulsion Sample Y
was sensitized markedly in comparison with emulsion Sample X, but it did
not prove feasible because of great fog occurring during storage at high
temperatures. The emulsion Sample Z not only increased in sensitivity to a
greater degree than emulsion Sample X, but also barely exhibited any
increase in fog or change in sensitivity during storage at high
temperatures.
While the invention has been described in detail and in terms of specific
embodiments thereof, it will be apparent that various changes and
modifications can be made therein without departing from the spirit and
scope thereof.
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