JPS63253349A - Silver halide photographic emulsion for direct positive - Google Patents

Abstract

PURPOSE:To obtain a photographic emulsion having high sensitivity and low fog level by combining a pyridinium salt having a specified compsn. with a weak electron acceptor having -0.90--1.00V reduction potential (ER) and >=+0.90V oxidation potential (EOX). CONSTITUTION:At least one kind of pyridinium salt expressed by formula I-III is(are)used in combination with an org. compd. having -0.90--1.00V ER and >=+0.90V EOX, as electron acceptor. In formulas I-III, R<1>-R<8> may be same or different to each other, each being H, alkyl group; R<1> with R<2>, R<2> with R<3>, or R<5> with R<6> may form a benzene ring; R is an alkyl group such as methyl, ethyl, sulfopropyl group; X<-> is an anion such as halide ion, sulfonic acid ion, etc.; n is 0 or 1. By this constitution, a photographic emulsion having high sensitivity and low fog level is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Field of Application The present invention relates to a direct positive silver halide photographic emulsion.
,90V to -1,00V and oxidation potential is +0.90V
The present invention relates to a direct positive silver halide photographic emulsion sensitized by a combination of the above electron-accepting organic compounds.

CB) Prior art and its problems Direct positive images are obtained using certain silver halide photographic emulsions. For example, there are photographic emulsions assembled from fogged silver halide and electron acceptors, as described in U.S. Pat. No. 3,501,307. In order to increase the sensitivity of this type of photographic emulsion, it is important to select conditions that provide capri.

Spectral sensitization techniques have also been used, and many cyanine dyes have been reported. However, what is important is that
The choice is the electron acceptor. The electron acceptor used is an organic desensitizing agent such as paraquat or a desensitizing dye such as pinacryptol yellow.
These are the above organic compounds. In general, the desensitizing dyes are superior to pyridinium salts, but they are disadvantageous in that they often cause coloring (color staining) due to residual dyes after development. or,
Pyridinium salts have the disadvantage of being susceptible to capri formation.

(C) Purpose of the Invention The present inventors have conducted intensive research to develop a direct positive silver halide photographic emulsion with high sensitivity and low fog level, and have found that the reduction potential (Ha) is -0,807 or more. If the oxidation potential (Box) is +o, sov or higher, ER2>: -0,90V to -1,00V and Box
It has been found that a combination of weak electron acceptors with a voltage of +0.90 V or more is suitable for that purpose.

(D) Constituent structure of the invention At least one pyridinium salt of the general formula
By using an organic compound with x of +0.90 V or more as an electron acceptor, a direct positive silver halide photographic emulsion with high sensitivity and low capri was obtained.

[1] Ell) [111)
In the formula, R, 1 to R8 may be the same or different, each represents hydrogen or an alkyl group, and R1 and R2 or R2 and R
3 or R'' and R6 may form a benzene ring.

R is an alkyl group, such as a methyl group, an ethyl group, or a sulfobyl group. X- is an anion and represents a halide ion, a sulfonate ion, or the like.

n is Ol or 1. Next, typical examples of pyridinium salts used in the present invention will be given.

■ 80s”- (3) CN 2H5 Br- The pyridinium salt used in the present invention can be easily synthesized by reacting the corresponding pyridine derivative with an alkylating agent. Next, the details will be described using a synthesis example. .

Synthesis of Compound (1) 3 t of 2-cyanopyridine and 10 ml of ethyl iodide were heated and dried for 8 hours. After cooling, the precipitated crystals were separated, washed with ether, and then dried.

mp 16B℃ (dec) Yield 2.52 compounds (
2) Synthesis of 4-cyanopyridine 1.04F and propane sultone 1.
22 f was heated at 80°C to 100°C for 2 hours.

The reaction mixture was crushed, washed with acetone and dried.

mp 280°C (dec) Yield 1.886F Synthesis of Compound (4) 1.04 f of 4-cya/pyridine and 2.28 f of n-butyl tosylate were heated at 160 to 170°C for 5 hours.

After cooling, the reaction mixture was crushed, washed with acetone, and dried.

mp 134-136°C Yield 2.6f Other pyridinium salts used in the present invention can also be easily synthesized according to the above example.

The pyridinium salt sensitizer used in the present invention has an ER of -0
,90V to -1,00V and Eox' is +0.90V or more. These sensitizers do not directly sensitize positive silver halide photographic emulsions by themselves, but are effective only when used in combination with pyridinium salts. The redox potential of these compounds was measured by cyclic portammetry.

The supporting electrolyte during the measurement was tetra n-butylammonium perchlorate (0.1M), and the solvent was acetonitrile. The reference electrode was SCB, and the working electrode was a stationary platinum electrode.

Next, typical examples of weak electron acceptors used in the present invention will be given.

Compound Sennin CHs 02N Compound B Compound C 2H5 Heat compound Compound E I- Absorption maximum (nm) of the above representative compound in methanol
, the redox potential was as follows.

Compounds AC were synthesized according to US Pat. No. 3,988.156.

Synthesis of Compound 3-cyanopyridine 3f and ethyl iodide 10yd were heated under reflux for 5 hours. After cooling, the precipitated crystals were collected and washed with ether. Yield 5.4 f mp 191-193#c/<
Synthesis of Compound B> 2.5-bismethylmercapto 1,3.4-thiadiazole 0.36 f and methyl-P-)sylate 0.742
was heated at 140-145°C for 2 hours. After cooling, it was washed twice with inclovir ether 10-. The residue was dissolved in ethanol 50°C, 3-edelrhodanine 3.22F,
6.07 f of triethylamine was added and the mixture was refluxed for 15 minutes. After cooling, the precipitated crystals were washed with ethanol and then recrystallized from acetonitrile.

mp182-182.5℃ Yield 4.7OfeOH λmax 417,405nm 5 (2-(3-methyl-5-methylmercapto-2,3-dihydro-1,3,4-?Asiazoliden)) obtained in this manner -3-Ethylrhodanine 0.319 and methyl-P-)sylate 0.749 were heated at 140-145°C for 2 hours. After cooling, they were washed hot with a small amount of inclovir ether. The residue was mixed with ethanol 10- To the mixture were added 0.7 F of 3-ethyl-2methyl-6-nitropenzothiazolinium Φ iodide and 0.41 F of rietheramine, and the mixture was heated under reflux for 15 minutes. After cooling, the precipitated crystals were collected, washed with ethanol, and then washed with 20 cm of hot methanol.

mp268°(dec) λmax510nm Yield o, sot These weak electron acceptors have a small effect when used alone, but show a remarkable effect when used in combination with a pyridinium salt.

In the present invention, a pyridinium salt and a sensitizer can be added to a silver halide photographic emulsion by a known method. For example, it can be added as a solution in a solvent such as methanol, ethanol, isopropanol, pyridine, dimethylformamide, acetone, water, etc. alone or in combination.

It can also be added to the emulsion using ultrasonic dispersion. Additionally, known methods for negative emulsions, such as U.S. Pat. No. 3,482,981;
No. 3,469,987, No. 3,649,28
No. 6, No. 3,485,634, No. 3,342,6
The methods described in No. 05 and No. 2,912,343 can also be used.

The amounts of the pyridinium salt and sensitizer used in the present invention vary depending on various factors of the silver halide photographic emulsion, but are preferably I x 10 = ~2 x 10
-” mole/mole Ag range.

Although the dye can be added to the emulsion at any stage of emulsion preparation, it is particularly preferred to add the dye immediately before coating.

Moreover, even if the order of addition of pyridinium salt and sensitizer is simultaneous,
Whichever comes first is fine.

Silver halide photographic emulsions used in the present invention include silver chloride, silver bromide, silver chlorobromide, silver iodide, silver chloroiodobromide, and silver iodobromide emulsions.

In order to obtain a highly sensitive direct positive silver halide photographic emulsion, a silver halide photographic emulsion containing 80 moles or more of bromide is preferred.

The silver halide photographic emulsion used in the present invention includes:
It includes both monodisperse and non-monodisperse,
Monodisperse ones are more preferable.

Further, the crystal habit of the silver halide photographic emulsion used in the present invention may be cubic or octahedral, but cubic is more preferred.

Furthermore, the grains of the silver halide photographic emulsion used in the present invention are preferably regular.

In the present invention, an emulsion may be used which has a nucleus for capturing free electrons inside the silver halide crystal and whose surface is capped with a chemical capping agent. The production of the emulsion for this disc is, for example,
U.S. Patent No. 3,367,778, U.S. Patent No. 3,632,3
No. 40 and No. 3,709,689.

The silver halide photographic emulsion used in the present invention is
Covered with a chemical capri agent. Methods of chemically imparting capri include, for example, Antoine Haute (Antoine Haute).
toine Hautot) and Henri Thorpe
Scianse Industry Photographic (Sci) by Henri 8aubenier
ence et Industries Photog
Favorable results can be obtained by using the method of chemical sensitization described in Vol. 28, pp. 57-65 (published in 1957).

The silver halide photographic emulsion used in the present invention can be given capri by using a reducing agent. Specific examples of the reducing agent include stannous chloride, thiourea dioxide, formalin, hydrazine and its derivatives, and amineborane.

The silver halide photographic emulsion used in the present invention can also be given a capri by using a gold compound.

Specific examples of the gold compound include chloroauric acid, potassium chloroaurate, potassium thiosulfate, and the like.

The silver halide photographic emulsion used in the present invention can also be given a capri by combining a reducing agent with a metal compound having a nobler potential than silver.

As specific examples of metal compounds having a nobler potential than silver potential, in addition to the above-mentioned gold compounds, platinum compounds such as potassium chloroplatinate, and iridium compounds such as potassium hexachloroiridate are used.

Furthermore, by using the above method in combination with a sulfur-containing sensitizer such as sodium thiosulfate or allylbuourea, or a thiocyanic acid compound such as potassium thiocyanate, a silver halide photographic emulsion can be fogged.

Examples of the protective colloid used in the present invention include natural products such as gelatin, albumin, agar, gum arabic, and alginic acid, and water-soluble synthetic resins such as polyvinyl alcohol, polyvinylpyrrolidone, and cellulose ether.

In the present invention, various additives such as stabilizers, brighteners, ultraviolet absorbers, hardeners, surfactants, preservatives, plasticizers, and matting agents can be included in the silver halide photographic emulsion. .

Examples of the support used in the present invention include d!
Resin films such as ethylene terephumerate and cellulose acetate, synthetic paper, and waterproof paper can be used. Also,
Paper laminated with plastic can also be used. If necessary, a subbing layer can be provided on these supports by a known method.

The light-sensitive material coated with the direct positive silver halide photographic emulsion of the present invention is processed using known processing baths such as development, fixing and bleaching, or a combination of these processing baths.

The present invention is characterized by two types of electron acceptors: Pi! Direct positive silver halide photography with high sensitivity and low fog level by combining a sensitizer with an Eox of +0.90V or more. The point is that an emulsion can be obtained. Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is of course not limited thereto.

(E) Example Example Control A silver iodobromide emulsion (2 mol l of iodine) was prepared using the control double run method. It was a monodispersed emulsion containing 95% by weight of particles within 30 inches of particle size.After precipitation and washing with water, gelatin was added and the pH was adjusted to 8.0.
Adjust pAg to 5.0 and add potassium chloroaurate 2 tq/
mde Ag was added and the mixture was heated at 60° C. for 2 hours. After that, adjust the pAg to 8.5 and pH to 5.0, divide the sample, and divide the pyridinium salt into 35011P/mole Ag.
was added. Furthermore, 200 tq/mole Ag of a sensitizer was added, a hardening agent and a surfactant were added, and a coating amount of 3.7 f/lri in terms of silver nitrate was applied to a paper support laminated with subbed polyethylene. It was coated with After drying, the progeny sample was cut to an appropriate size, exposed through a wedge with a density difference of 0.15, developed at 20°C for 90 seconds using Kodak Company D-72 developer, and then processed using an acidic fixer. After fixing, wash with water and dry. As a result of concentration measurement,
Table 1 was obtained.

S in the table is a value measured at an optical density of 0.75, and is expressed as a relative value with the case of cypyridinium salt alone being 100. Furthermore, Dmin represents the minimum density and fog level.

Table 1 As is clear from Table 1, the sensitizer of the present invention has no sensitivity by itself, but when combined with a pyridinium salt provides a silver halide photographic emulsion with high sensitivity and low capri.

(F) Effect of the invention The feature of the present invention is that it combines a pyridinium salt, which is a strong electron acceptor, and a weak electron acceptor, whose BR is -0.90V to -i, o ov and Eox is 0.90V or more. The goal is to obtain a direct positive silver halide photographic emulsion with high sensitivity and low capri.

Claims (1)

[Scope of Claims] 1) At least one pyridinium salt of general formulas [I] to [III] and an electron-accepting organic compound having a reduction potential of -0.90V to -1.00V and an oxidation potential of +0.90V or more. A direct positive silver halide photographic emulsion characterized by containing at least one compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I]▲There are mathematical formulas, chemical formulas, tables, etc.▼[II]▲There are mathematical formulas, chemical formulas, tables, etc.▼[III] [In the formula, R^1 to R^8 are It can be the same or different,
Each represents hydrogen or an alkyl group, and R^1 and R^2, R^2 and R^3, or R^5 and R^6 may form a benzene ring. R represents an alkyl group. X^- is an anion, and n is 0 or 1. ]