JPS585421B2 - Method for producing direct positive silver halide photographic emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a direct positive silver halide photographic emulsion with high sensitivity and high contrast.

The direct positive silver halide photographic emulsion referred to in the present invention is a silver halide emulsion consisting of fogged silver halide grains and an electron acceptor, for example, British Patent No. 723,01
9 and US Pat. No. 3,501,307.

Many attempts have been made to date to increase the sensitivity of direct positive silver halide emulsions.

For example, in the specification of Japanese Patent Publication No. 46-25953, it is stated that ``at least about 55 mol% is silver bromide, at least about 10 mol% is silver chloride, and about 5 mol% or less is silver iodide. Silver halide grains having silver bromide grains on the grain surface comprising silver bromide in an amount corresponding to about 2.5 to 50 mol% of the total silver halide contained in the grains. A direct positive photographic silver halide emulsion characterized by consisting of grains was proposed.

However, although this emulsion had kink mark desensitization resistance, its sensitivity was low.

Further, in Japanese Patent Publication No. 47-2755, [In a fogged direct positive emulsion consisting of silver halide grains and having an electron acceptor or a halogen acceptor adsorbed on the surface of the grains, the above-mentioned The halogen content of silver halide is at least 50
and the emulsion contains 0.01 to 0.2 mole of water-soluble bromide per mole of silver, or 0.01 to 0.2 mole of water-soluble bromide per mole of silver. An improved direct positive silver halide emulsion characterized by the addition of 0.002 to 0.03 mole of water-soluble iodide per mole of silver was proposed.

However, although this emulsion had a high maximum density, it was insufficient in terms of sensitivity.

Furthermore, in the specification of Japanese Patent Publication No. 46-43431, it is stated that ``the particles consist of silver halide grains, and at least 50% of the silver halide is
The mole percent is bromide, the silver halide grains contain electron acceptors, and are a direct positive photographic emulsion uniformly fogged with a reducing agent and a metal compound that is more electrically positive than silver; Silver halide grains contain, apart from any iodide present within the grains, as mixed silver halide.
A direct positive photographic emulsion based on silver halide, characterized in that it is in contact with 0.2 to 3 mole % of water-soluble iodide, has been proposed.

However, although this emulsion was quite favorable in terms of sensitivity, it had the drawback of low contrast.

The present inventors have conducted extensive research to obtain a direct positive silver halide photographic emulsion with high sensitivity and high contrast while taking into consideration the drawbacks of the prior art described above. As a result, the following emulsion manufacturing method is preferred. I discovered that.

That is, in a method for producing a direct positive silver halide emulsion comprising fogged silver halide grains containing at least 90 mol % of bromide and having electron acceptors adsorbed on the surface of the grains, excess salts of the emulsion are used. Water-soluble bromide and water-soluble silver necessary to form 1 mol % to 10 mol % of silver bromide per 1 mol of silver halide after reducing the amount of water and before the end of the fogging process. This is a method for producing a direct positive silver halide photographic emulsion, which is characterized by adding a salt.

In addition to the above emulsion manufacturing method, before adding water-soluble bromide and water-soluble silver salt, per mole of silver halide,
By adding 0.002 mol to 0.03 mol of water-soluble iodide, a method for producing a direct positive silver halide photographic emulsion with high contrast and higher sensitivity has been discovered.

An object of the present invention is to provide a method for producing a direct positive silver halide photographic emulsion with high sensitivity and high contrast.

Other objects of the invention will become apparent from the following description.

The manufacturing process of silver halide photographic emulsion is as follows.

■Emulsification process - A process in which water-soluble silver salt and water-soluble halide are mixed in the presence of a protective colloid to generate and grow silver halide grains.

(2) Precipitation and water washing process - A process for reducing excess salts (eg, Na+, Ni+, NO3-, Cr, Br-, etc.).

■Chemical ripening process - chemical sensitizers and fogging agents
A process that introduces sensitizing nuclei and fog nuclei onto silver halide grains.

■Final preparation process - Adding sensitizing dyes, additives (e.g. stabilizers, development accelerators, etc.), hardeners, surfactants, etc.
Process for final adjustment of pl, pAg, etc.

In the present invention, after reducing excess salts and before the end of the fogging process, the water-soluble By adding a silver salt, high sensitivity and
A direct positive silver halide photographic emulsion with high contrast can be obtained.

Here, the stages from reducing excess salts to the end of the fogging process are from the time when the above-mentioned ■ precipitation, water washing, and redissolution are completed to ■ completion of the chemical ripening process. This is the stage just before.

Preferably, the water-soluble bromide and water-soluble silver salt are added in the form of an aqueous solution.

The order of addition may be either first or at the same time.

If the amount of silver bromide formed was less than about 1 mol % or more than about 10 mol % per mol of silver halide, sufficient high contrast could not be obtained.

Specific examples of water-soluble bromides used in the present invention include ammonium bromide, potassium bromide, sodium bromide, and the like.

Further, as specific examples of water-soluble silver salts used in the present invention,
Examples include silver nitrate and silver perchlorate.

In the present invention, before adding water-soluble bromide and water-soluble silver salt, 0.2 mol % to 3.0 mol % is added per mol of silver halide.
By adding water-soluble iodide corresponding to mol%
Further, it is possible to obtain a silver halide photographic emulsion for liquid-prepared positives with high sensitivity and high contrast.

The amount of water-soluble iodide added is 0.00% per mole of silver halide.
When A is 2 mol % or less, the effect of increasing sensitivity is small, whereas when A is 3.0 mol % or more, sufficient contrast cannot be obtained.

The timing of addition must be before water-soluble bromide and water-soluble silver salt are added, so that iodide ions are located on the surface of silver halide grains after water-soluble iodide is added. If you do, the effect will be great.

That is, as shown in Example 2 below, addition of water-soluble bromide near the end of emulsification is also included within the scope of the present invention.

Specific examples of water-soluble iodides used in the present invention include ammonium iodide, potassium iodide, sodium iodide, lithium iodide, and the like.

In the present invention, the expression "per mole of silver halide" means:
It refers to 1 mole of silver halide containing at least 90 mol% bromide produced during the first ripening, and does not include silver halide produced when added later.

The silver halide emulsion used in the present invention is a silver chloride, silver iodobromide, silver chloroiodobromide, or silver bromide emulsion consisting of at least 90 mole percent bromide.

Among these, silver iodobromide and silver chloroiodobromide emulsions give more preferable results.

The silver halide emulsion used in the present invention may be produced by any of the acidic method, neutral method, or ammonia method, but the ammonia method is particularly preferred because the above-mentioned effects are remarkable. Results Obtained 0 The silver halide emulsion used in the present invention is a monodisperse emulsion, and it also includes those that are not monodisperse, but monodisperse emulsions are preferred.

Furthermore, the silver halide emulsions used in the present invention may be regular or irregular.
(re-gular) ones are also included, but regular ones are preferable.

Silver halide emulsions used in the present invention also include those prepared by the method described in US Pat. No. 3,367.778, for example.

In this type of emulsion, the interior of the grain is chemically sensitized or fogged and covered with an outer shell.

The electron acceptor used in the present invention is characterized by its polarographic half-wave potential, ie its redox potential determined polarographically.

Electron acceptors useful in the present invention are those in which the sum of polarographic anode potential and polarographic cathode potential is positive.

Methods for measuring these redox potentials are described, for example, in US Pat. No. 3,501,07.

A particularly effective electron acceptor for use in the present invention is the imidazo(4,5-b)quinoosaline cyanine dye described in Belgian Patent No. 660,253.

Another particularly effective electron acceptor is U.S. Pat.
It is an indole cyanine dye described in specifications such as No. 14,796 and No. 3,505,070.

Among these electron acceptors, preferred ones are represented by the following general formula (I).

In the formula, L is -CH=, -C(CH3)=.

It means a methine bond such as C(CaH5)=A.

A is an aryl group (e.g., phenyl, p-tolyl,
p-methoxyphenyl, p-ethoxyphenyl, p-chlorophenyl, naphthyl, etc.) or a heteroaromatic ring group (for example, pyridinyl, pyrrolyl, etc.).

R2 and R3 are a hydrogen atom or a halogen atom (eg, Br, CI, etc.), or each represents an atomic group necessary to form an aromatic ring having 6 carbon atoms together.

R1 is an alkyl group (e.g., methyl, ethyl, propyl, etc.), an A-substituted alkyl group (e.g., γ-sulfopropyl, ω-sulfobutyl, β-carboxyethyl, γ-carboxypropyl, etc.), an aralkyl group (e.g., benzyl, phenethyl, etc.), alkenyl groups (eg, allyl, propenyl, butyryl, etc.), or aralkyl groups (eg, propargyl, butynyl, etc.).

R41R5 each represents an alkyl group, a substituted alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, or an aryl group.

R6 is a hydrogen atom or a halogen atom, or R1
Together with, it represents an alkylene group such as trimethine or dimethine.

R7 represents a halogen atom, a cyan group, or a nitro group, and a is 0 or an integer of 1 to 3.

X represents an anion, preferably an acid anion such as chloride, bromide, iodide, p-toluenesulfonate, thiocyanate, sulfonate, methyl sulfate, ethyl sulfate, perchlorate.

Another preferable electron acceptor is represented by the following general formula (I).

In the formula, R7,n, R4, R5, L, and X are each as described above in general formula (I).

R8°Ro each represents a halogen atom, an alkyl group, a substituted alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, or an aryl group.

Rlo has the same meaning as R4.

Another preferable electron acceptor is represented by the following general formula (■).

In the formula, A+R1+R2+R3+R6+L+X are each as described above in general formula (I).

R11 has the same meaning as ARl, and m represents 0 or 1.

Z is a nonmetallic atomic group necessary to complete the heterocyclic nucleus used in cyanine dyes, and specific examples of the heterocyclic nucleus include benzothiazole nuclei (e.g., benzothiazole,
5-chlorobenzothiazole, 5-methylbenzothiazole, 5-phenylbenzothiazole, 5-methoxybenzothiazole, 6-nitrobenzothiazole, etc.),
naphthothiazole core (e.g. α-naphthothiazole,
β-naphthothiazole, 8-methoxy-α-naphthothiazole, etc.), benzoxazole nuclei (e.g., benzoxazole, 5-chlorobenzoxazole, 5-methylbenzoxazole, 5-phenylbenzoxazole, 5-methoxybenzoxazole, 6-nitrobenzoxazole, etc.) naphthoxazole nucleus (e.g., α-naphthoxazole, β-naphthoxazole, etc.), 2-quinoline nucleus (e.g., quinoline, 3-methylquinoline, 5-methylquinoline, 6-chloroquinoline, 6
-Medoxyquinoline, etc.), 4-quinoline nucleus (e.g., quinoline, 6-medoxyquinoline, etc.), 3,3-dialkyl-3H-indole nucleus (e.g., 3,3-dimethyl-3H-indole, 3, 3-dimethyl-5-nitro-
3H-indole, etc.), 3,3-dialkyl-3H-
Pyrrolo(2,3-b)pyridine nucleus (e.g., 3°3-dimethyl-3H-pyrrolo[2,3-b]pyridine, 3,3
-diethyl-3H-pyrrolo[2,3-b)pyridine, etc.]
etc.

Another preferred electron acceptor is the halogenated cyanine dye described in US Pat. No. 3,501,310.

These can be obtained by reacting a cyanine dye with a halogenating reagent (eg, halogen, N-chlorosuccinimide, N-promosuccinimide, N-iodosuccinimide, etc.) in an alcohol solution.

In the present invention, the electron acceptor is preferably used in a concentration ranging from 0.1 g to 2.0 g per mole of silver halide.

More preferably Ao, the concentration is in the range of 2g to 0.6g.

A specific example of the electron acceptor used in the present invention is A1.1'-dimethyl-2,2'-diphenyl-3,3
'-Indolocarbocyanine bromide, 2.2'-
V-p-methoxyphenyl-1,1'-dimethyl-3,
3' ~ indolocarbocyanine bromide, 1,1'
-dimethyl-2,2',8-triphenyl-3,3'-
Indolocarbocyanine verchlorate, ■.

3-Diallyl-2-[2-(9-methyl-3-carbazolyl)vinyl]imidazo(4,5-t))quinoxalium p-t-luenesulfonate, ■.

3-diethyl-1/-2/-phenyl imidazo[4°5-b]quinoxalino 3'-indolocarbocyanine iodide, 1. l', 3.3'-tetraethylimidazo[4,5-b]quinoxalinocarbocyanine chloride, 1.1', 3.3'-tetramethyl-2-phenyl-3-indropyrrolo[2゜3- b] Pyridocarbocyanine iodide, 1.1', 3,3.3',
3'-hexamethylpyrrolo(2,3-b)pyridocarbocyanine verchlorate, 1.1',3,3-tetramethyl-5-nitro-27-phenylindo-3'-indocarbocyanine iodide , 1.1', 3,3
,3',3'-hexamethyl-5,5'-dinitroindocarbocyanine p-toluenesulfonate, 3'-
Ethyl-1-methyl-2-phenyl-6'-nitro-3
-Indrothiacarbocyanine p-toluenesulfonate, pinacryptol yellow, 5-m-nitrobenzylidene rhodanine, 5-m-nitrobenzylidene-
Examples thereof include 3-phenylrhodanine, iodide of 1°3-diethyl-6-nitrothia-2'-cyanine iodide, and the like.

In the present invention, in addition to the electron acceptor, a known sensitizing dye can also be used in combination.

Favorable results can be obtained by combining known cyanine dyes or rhodanine dyes with electron acceptors.

The direct positive silver halide emulsion used in the present invention can be fogged with light or with a chemical fogging agent.

As a method of imparting such fog, for example, the method of Autoine Hautot
and Henri Sauvenel
Science Industrie Photography (r) by Science Industries Photography
Photographiques) 28+1-23,
and 57-65 (1957) are effective.

The direct positive silver halide emulsion used in the present invention can be produced by using a combination of a ring agent and a metal compound having a more noble potential than silver, as described in, for example, U.S. Pat. No. 3,501,307. It is preferable that

Specific examples of the ring-forming agent used in the present invention include thiourea dioxide, hydrazine derivatives, formaldehyde, stannous chloride, and amineborane.

Further, specific examples of metal compounds having a more noble potential than silver used in the present invention include gold compounds (e.g., chloroauric acid, potassium chloroaurate, etc.), platinum compounds (e.g., potassium chloroplatinate, sodium chloroplatinate, etc.). etc.), iridium compounds (
Examples include potassium hexachloroiridate, iridium, tribromide, etc.).

The direct positive silver halide emulsion used in the present invention is preferably fogged with a metal compound having a more noble potential than silver.

Specific examples of metal compounds having a more noble potential than silver are as described above.

The direct positive silver halide emulsion used in the present invention can be produced using the above method, a sulfur-containing compound (for example, sodium thiosulfate, potassium thiosulfate, allylthiourea, etc.), or
Thiocyanate compounds (e.g. potassium thiocyanate,
It can also be fogged by combining with ammonium thiocyanate, etc.).

Protective colloids for the direct positive silver halide emulsion used in the present invention include gelatin, modified gelatin, albumin, agar, gum arabic, natural products such as alginic acid, polyvinyl alcohol, polyvinylpyrrolidone, acrylamide, acrylic acid, and vinylimidazole. Examples include water-soluble synthetic resins such as copolymers of.

The direct positive silver halide emulsion used in the present invention contains stabilizers, development accelerators, brighteners, color couplers, surfactants, hardeners, dye removal improvers, and thickeners, as necessary. etc. can be included.

Direct positive halogenation produced according to the invention.

The silver emulsion can be prepared on a suitable support, glass, cellulose acetate film, polyethylene terephthalate film, paper, barique coated paper, polyolefin (e.g. polyethylene,
(polypropylene, etc.) coated on something like paper.

These supports may be corona treated by a known method and, if necessary, may be undercoated by a known method.

A light-sensitive material coated with the direct positive silver halide emulsion produced according to the present invention can be processed in known developing, fixing, bleaching, etc. baths.

A feature of the present invention is that a direct positive silver halide photographic emulsion with high sensitivity and high contrast can be obtained.

The present invention will be described in detail below with reference to Examples, but it is of course not limited thereto.

Example 1 A raw emulsion was prepared according to the following formulation.

D Keep acetic acid A at 40°C, add B while stirring vigorously, and add 1
After a few minutes, C was added and the mixture was aged at 40°C for 9 minutes.

Thereafter, D was added to adjust the pH to 3.5, and the mixture was precipitated by a flocculation method, washed with water, and gelatin was added to dissolve it again.

The raw emulsion was a silver chloroiodobromide emulsion having an average grain size of 0.45 microns and consisting of at least 90 mole percent bromide.

After adding potassium bromide aqueous solution and silver nitrate according to the recipe in Table 1, the pH was adjusted to 6.5 and the pA
g to 6.2 and 0.2 mQ/m of thiourea dioxide
o]eAg was added and aged at 60°C for 60 minutes.

Further, 2n9/mole Ag of potassium chloroaurate was added, and after aging at 60°C for 60 minutes, the pAg was adjusted to 8.0. pH
was adjusted to 5.0.

each, 5-m-nitrobenzylidene rhodanine 300n
? /moIe Ag was added, a hardener and a surfactant were added, and the mixture was coated on a polyethylene terephthalate film to give a coated silver amount of 2.6 g/m2 in terms of Ag.

After drying, each sample was exposed through a wedge with a density difference of 0.15, then developed in Kodak Formula D-72 developer at 20° C. for 90 seconds, fixed, washed with water, and dried.

The results of concentration measurements are shown in Table 1.

Relative sensitivity (S) is the relative value of the reciprocal of the exposure amount at density 1.0, and contrast (γ) is the relative value at density 0.4 and density 1.0.
The maximum density (Dmax) and the minimum density (Dmin) include the base density.

As is clear from Table 1, Sample 3 according to the present invention has higher sensitivity and higher contrast than Samples 1 and 2, and has a lower Dmin.

In addition, even when compared with sample 4, it showed almost the same sensitivity, and γ
and Dmax are larger than those of sample 4.

Similarly, when the amount of KBr added and the amount of AgNO3 added were changed, it was found that the effect of the present invention is significant when the amount of AgBr formed is between 1.0 mol% and 10 mol%. Ta.

Example 2 A raw emulsion was prepared according to the following formulation.

Emulsion 2-A 10% potassium iodide aqueous solution 4ml H Acetic acid E was kept at 40°C, F was added while stirring vigorously, 4ml
Aged at 0C for 10 minutes, added G, 5 minutes later added H, adjusted the pH to 3.5, precipitated by flocculation method, washed with water, added gelatin and redissolved. .

The raw emulsion was a silver chloroiodobromide emulsion having an average grain size of 0.45 microns and consisting of at least 90 mole percent bromide.

To this, 0.05 mol of KB per mol of silver halide
Add r and 0.05 mol of AgNO3, adjust the pH to 6.5 and pAg to 4.9, and add 3ny of potassium chloroaurate.
/moleAg was added and aged at 60°C for 100 minutes,
pAg, s, o, and pi were adjusted to 5.0.

Each Pinacryptol Yellow 300IQ/mol
e Ag was added, a hardener and a surfactant were added, and the polyethylene terephthalate film was converted to 2.
It was coated to give a coated silver amount of 6 g/m2.

(Sample 5) Emulsion 2-B O or oi mol of iodine per mol of silver halide was added to the raw emulsion prepared in the same manner as the formulation of Emulsion 2-A except that the potassium iodide aqueous solution of G was not added. After adding an aqueous potassium chloride solution and leaving it for 10 minutes at 40°C, 0.05 mol of KBr and 0.05 mol of AgNO3 were added per 1 mol of silver halide. Prepare an emulsion and apply polyethylene terephthalate with the same coating amount.
applied to film.

(Sample 6) Emulsion 2-C Using the raw emulsion prepared in the same manner as Emulsion 2-B, KI was not added before adding KBr and AgNO3, and the other conditions were the same as Emulsion 2-B. A positive emulsion was prepared and coated on polyethylene terephthalate film at the same coating weight.

(Sample 7) Emulsion 2-D Using the original emulsion prepared in the same manner as Emulsion 2-B, the order of addition of KBr and AgBr and addition of KI was reversed, and the rest was the same as Emulsion 2-B. A direct positive emulsion was prepared and coated on polyethylene terephthalate film at the same coverage.

(Sample 8) After drying, the same treatment as in Example 1 was carried out, and the second
The results shown in the table were obtained.

As is clear from Table 2, Samples 5 and 6 of the present invention have lower γ and Dmax than Sample 7.

Dmin is almost the same, and is 3.2 times and 4 times, respectively.
．． It has five times the sensitivity.

On the other hand, sample 8 has a sensitivity of 3.4 compared to sample 7.
However, the contrast has decreased and is inferior to Samples 5 and 6.

As is clear from this example, if water-soluble iodide is added before adding water-soluble bromide and water-soluble silver salt, a direct positive silver halide emulsion with high contrast and higher sensitivity can be obtained.

Similar experiments have revealed that the amount of water-soluble iodide added is preferably 0.002 mol to 0.03 mol per mol of silver halide.

Example 3 This example relates to the halogen composition of an emulsion.

The following raw emulsion was prepared using the double run method and controlling pAg.

Emulsion 3-A Silver chlorobromide emulsion consisting of 80 mol% bromide and 20 mol% chloride (average grain size 0.3μ) Emulsion 3-B Salt consisting of 95 mol% bromide and 5 mol% chloride Silver bromide emulsion (average grain size 0.3μ) Emulsion 3-C Silver bromide emulsion (average grain size 0.3μ) Emulsion 3-D Silver iodobromide consisting of 98 mol% bromide and 2 mol% iodide Emulsion (average particle size: 0.3 μm) The particle size distributions of the four raw emulsions described above were almost the same.

These raw emulsions were precipitated by a flocculation method, washed with water, and redissolved.

To these were added 0.005 mol of KI per mol of silver halide, and then 0.01 mol of KI per mol of silver halide.
5M KBr and 0.015M AgNO3 were added to adjust the pH to 6.5 and pAg to 4.9.

Add potassium chloroaurate 3 mg/mole Ag, 6
Aged for 0°C, ioo minutes, pAg: 8.0°, pH: 5.0°C.
Adjusted to 0.

Pinacryptol Yellow 300ng/mole each
Ag was added, a hardening agent and a surfactant were added, and the paper was laminated with polyethylene.
Coating was carried out so that the amount of silver coated was m2.

For comparison, a direct positive emulsion prepared in the same manner as in this example, except that KBr and AgNO3 were not added, was applied to polyethylene-laminated paper at a coated silver amount of 16 g/m2 in terms of Ag. It was applied so that

After drying, the same treatment as in Example 1 was performed, and the results shown in Table 3 were obtained.

As is clear from Table 3, emulsions 3-B, 3-
In C, 3-D, a significant increase in contrast due to the addition of KBr and AgNO3 was observed, and the sensitivity was also increased, whereas in Emulsion 3-A, although an increase in sensitivity was observed, there was little increase in contrast.

As shown in this example, the addition of water-soluble bromide and water-soluble silver salt is extremely effective in direct positive silver halide photographic emulsions containing at least 90 mol % or more of bromide.

Example 4 This example relates to the combined use of an electron acceptor and a sensitizing dye.

A raw emulsion was prepared using the same recipe as in Example 1.

It was precipitated by the flocculation method, washed with water, and then redissolved by adding gelatin.

To this emulsion, 0.01 mol of potassium iodide aqueous solution was added per mol of silver halide, and after standing at 40°C for 10 minutes, 0.03 mol of KBr per mol of silver halide was added.
and 0.03 mol of AgNO3 to adjust the pH to 6.5.
Adjust pAg to 4.9 and add potassium chloroaurate 3mg/
fO1eAg was added, aged at 60°C for 100 minutes, and p
Ag 8.0. The pH was adjusted to 5.0.

This was divided into 4 equal parts, and a sensitizing dye having the following structural formula was added according to the recipe shown in Table 4.

Pinacryptol yellow (300 mg/mole Ag) was added to each sample, a hardener and a surfactant were added, and the coating was applied to a polyethylene terephthalate film to give a coated silver amount of 2.6 g/m2 in terms of Ag.

After drying, the same treatment as in Example 1 was performed, and the results shown in Table 4 were obtained.

As is clear from Table 4, the combined use of an electron acceptor and a sensitizing dye increases the sensitivity by 3 to 4 times, and increases γ, Dmax
, did not have much influence on Dnin.

As is clear from this example, it was found that the combination of an electron acceptor and a sensitizing dye is very preferable for increasing sensitivity.

Example 5 This example relates to a combination of electron acceptors.

A raw emulsion was prepared using the same recipe as in Example 1.

It was precipitated by the flocculation method, washed with water, and then redissolved by adding gelatin.

To this emulsion, 0.008 mol of potassium iodide aqueous solution was added per 1 mol of silver halide, and the mixture was left to stand at 40°C for 10 minutes. Add .015 mol of AgNO3 and adjust the pH
Adjust the pAg to 6.5 and pAg to 4.9, add 2 m9/mole Ag of potassium chloroaurate, and heat at 60C, 120C.
Aging for 8.0 minutes. The pH was adjusted to 5.0.

This was divided into four equal parts, and an electron acceptor having the following structural formula was added according to the recipe in Table 5.

Pinacryptol Yellow 300mg/mol each
e Add Ag, add a hardening agent and a surfactant, and add 2-
It was coated to give a coated silver amount of 69/m2.

After drying, the same treatment as in Example 1 was performed, and the results shown in Table 4 were obtained.

As is clear from Table 5, the combined use of pinacriptol yellow and electron acceptors (d) to (f) increased the sensitivity to 8.
It increased by ~9 times, and did not significantly affect γ, Dmax, and Dmin.

As is clear from this example, by combining an electron acceptor, a direct positive silver halide photographic emulsion with higher sensitivity can be obtained.

Example 6 This example concerns the timing of addition of water-soluble bromide and water-soluble silver salt.

Emulsion 6-A Using the double run method and controlling pAg, 9
A silver chlorobromide emulsion (average grain size 0.3 μm) consisting of 5 mol % bromide and 5 mol % chloride was prepared.

Before flocculating it, 0.05 mol of KBr and 0.05 mol of AgN were added per mol of silver halide.
After adding O2 and leaving at 60°C for 5 minutes, after cooling,
It was precipitated by the flocculation method, washed with water, and then redissolved by adding gelatin.

This raw emulsion was adjusted to pH 6.5. Adjust pAg to 4.9, add potassium chloroaurate 3m9/moIe Ag,
Aging at 60°C for 100 minutes until the pAg was 8.0. pH to 5
．． Adjusted to 0.

Add to this Pinacryptol Yellow 300mg/mo
le Ag, hardener and surfactant were added, and the polyethylene terephthalate film was made into a polyethylene terephthalate film with 2
．． It was coated to give a coated silver amount of 6 g/m2.

Emulsion 6-B After redissolving KBr and AgNO3 addition timing, pH 9pA
A direct positive emulsion was prepared in the same manner as Emulsion 6-A, except before g adjustment, and coated on a polyethylene terephthalate film at the same coating weight.

Emulsion 6-C A direct positive emulsion was prepared in the same manner as Emulsion 6-A, except that KBr and AgNO3 were added 40 minutes after the start of the second ripening, and a polyethylene terephthalate film was coated with the same coating amount. It was applied to.

Emulsion 6-D A direct positive emulsion was prepared in the same manner as Emulsion 6-A, except that KBr and AgNo3 were added after the completion of the second ripening, and was applied to a polyethylene terephthalate film in the same coating amount. .

After drying, the same treatment as in Example 1 was performed, and the results shown in Table 6 were obtained.

As is clear from Table 6, the timing of addition of water-soluble bromide and water-soluble silver salt is preferably after precipitation and water washing until the end of the second ripening.

That is, Samples 26 and 27 of the present invention have higher sensitivity, larger γ, and smaller Dmin than Sample 25, but Sample 28 has lower sensitivity and almost the same γ than Sample 25. Although the Dmin was slightly decreased, the photographic characteristics were inferior to those of Samples 26 and 27.

Example 7 A raw emulsion was prepared according to the following formulation.

Keep L acetic acid ■ at 40℃, add J while stirring vigorously, and add 1
Add particle size K, age at 40° C. for 10 minutes, add L, adjust pH to 3.5, and cool.

After precipitation, the precipitate was washed with water, and gelatin was added to dissolve the precipitate again.

The raw emulsion was a silver chloroiodobromide emulsion having an average grain size of 0.3 microns and consisting of at least 90 mole percent bromide.

To this was added 0.005 mol of potassium iodide aqueous solution per 1 mol of silver halide, and the mixture was left to stand at 40°C for 10 minutes.
015 mol of AgNO3 to pH 7.0, p
Adjust Ag to 4.6 and add potassium chloroaurate 1mg/m
ole Ag was added, aged at 60°C for 100 minutes, and p
Ag was adjusted to 8.0° and pH to 6.0.

Sensitizing dye (g) with the following structural formula: 400 mg/mole A
Add g and Vinacrypt-μ・Yellow 200mg/m
Add ole Ag, add hardener and surfactant, and add Ag to paper containing black pigment in the polyethylene laminate layer.
The amount of silver coated was 1.0 g/m2.

After drying, the following treatment was carried out in order to use it for a diffusion transfer type offset printing plate described in Japanese Patent Publication No. 48-30562.

That is, palladium sulfide sol was applied by the method described in Example 3 of Japanese Patent Publication No. 48-30562.

The sheet obtained in this way is photographed in an enlarged manner with a plate-making camera, and the same processing as in Example 1 of the same specification is performed.
It was possible to print more than one copy.

Example 8 A raw emulsion was prepared according to the following formulation.

While keeping the P acetate M at 40°C and stirring vigorously, N and 0 were added simultaneously over 100 minutes, during which time the pAg was increased to 8.
I kept it at 2.

Immediately after the addition, P was added to adjust the ApH to 35, precipitate by flocculation method, wash with water, add gelatin and redissolve.

This raw emulsion has an average grain size of 0.45μ, more than 95% by weight of the grains are within ±30% of the average grain size, the crystal habit is cubic, and 90% by weight of regular grains.
The above silver bromide emulsion was obtained.

To this was added 0.01 mol of potassium iodide aqueous solution per 1 mol of silver halide, and after leaving it for 10 minutes at 40°C, 0.05 mol of KBr and 0.05 mol of potassium iodide per mol of silver halide were added.
Add mol of AgNO3 to pH 6.5 and pAg to 4
．． Potassium chloroaurate 1 mg/mole
Add Ag and heat to 60°C.

Aged for 80 minutes and brought the pAg to 8.0. The pH was adjusted to 5.5.

In addition, 350 mg/m of electron acceptor (H) with the following structural formula
ole Ag was added.

Next, Pinacryptol Yellow 300 mg/mole Ag was added and the magenta coupler 1-(2,4,6-trichlorophenyl)-3°3'
- Add an emulsified dispersion containing (2",4"-di-t-amylphenoxy-acetamide)benzimidazo-5-pyrazolone, add a hardening agent and a surfactant, and add to the polyethylene-laminated paper. Coated.

The dried sample was exposed, color developed, processed in a bleach-fix bath, and washed with water to give a magenta direct positive image.

Example 9 A raw emulsion was prepared according to the following formulation.

Keep T acetic acid Q at 35°C, add i while stirring vigorously, and add 3
Add particle size S, age at 35° C. for 15 minutes, add T, adjust pH to 3.5 and cool.

After precipitation, the precipitate was washed with water, gelatin was added, and the mixture was redissolved.

The raw emulsion was a silver chloroiodobromide emulsion having an average grain size of 0.3 microns and consisting of at least 90 mole percent bromide.

To this, 0.005 mol of potassium iodide aqueous solution was added per 1 mol of silver halide, and the solution was left at 40°C for 10 minutes.
Add 1 mol of AgNO3 to pH 6.5, pAg
was adjusted to 4.9, and potassium chloroaurate was added to 2 mg/mol.
e Ag was added, aged at 60C for 120 minutes, and pAg
The pH was adjusted to 8.0° and 5.0.

Sensitizing dye (i) with the following structural formula 400mg/mole A
Add g and Pinacryptol Yellow 200mg 7m
ole, hardener and surfactant, to polyethylene terephthalate film, calculated as Ag, 3.
Coating was carried out so that the amount of coated silver was 6 g/n.

After drying, the samples were exposed through a wedge with a density difference of 0.15, then developed in Kodak formulation D-85 Lith type developer at 20C for 8 minutes, fixed, washed with water and dried.

As a result of concentration measurement, the following values were obtained.

Dmax〉4. Dmin=0.03. γ=11° The direct positive emulsion of this example clearly exhibited the Liss effect.

Further, this emulsion can contain a polyoxyethylene compound such as polyethylene glycol, and can also contain a development accelerator to shorten the development time.

Claims (1)

[Scope of Claims] 1. A method for producing a direct positive silver halide emulsion comprising fogged silver halide grains containing at least 90 mol % of bromide and having an electron acceptor adsorbed on the grain surface, After reducing the excess salts in the emulsion and before the end of the fogging process, the water-soluble amount necessary to form 1 mol % to 10 mol % of silver bromide per mol of silver halide. A method for producing a direct positive silver halide photographic emulsion, which comprises adding bromide and a water-soluble silver salt. 2. A method for producing a direct positive silver halide photographic emulsion according to claim 1, which is fogged by the combined use of a reducing agent and a metal compound having a more noble potential than silver. 3. A method for producing a direct positive silver halide photographic emulsion according to claim 1, which is fogged with a metal compound having a more noble potential than silver without using a reducing agent in combination. 4. Production of a direct positive silver halide photographic emulsion according to claim 1, 2, or 3, in which a sensitizing dye is adsorbed on the grain surface in addition to an electron acceptor. Method. 5. In a method for producing a direct positive silver halide emulsion comprising fogged silver halide grains containing at least 90 mol % of bromide and having electron acceptors adsorbed on the grain surface, excess salts of the emulsion are removed. Water-soluble bromide and water-soluble silver salt necessary to form 1 mol % to io mol % of silver bromide per mol of silver halide after the reduction and before the end of the fogging process. and before adding the water-soluble bromide and the water-soluble silver salt, 0.002 mol to 0.03 mol of water-soluble iodide per mol of silver halide is added. A method for producing a positive silver halide photographic emulsion. 6. A method for producing a direct positive silver halide photographic emulsion according to claim 5, which is fogged by the combined use of a reducing agent and a metal compound having a more noble potential than silver. 7. A method for producing a direct positive silver halide photographic emulsion according to claim 5, which is fogged with a metal compound having a more noble potential than silver without using a reducing agent in combination. 8 Claims 5, 6, or 7 in which a sensitizing dye is adsorbed on the surface of the particles in addition to an electron acceptor.
A method for producing a direct positive silver halide photographic emulsion as described in .