JPS63220133A - Silver halide photographic emulsion for direct positive - Google Patents

Abstract

PURPOSE:To obtain a low-fogging silver halide photographic emulsion for direct positives having high sensitivity by incorporating at least one kind of specific org. desensitizers into the emulsion. CONSTITUTION:The novel org. desensitizers to be used are the compds. expressed by formulas I and II. In formulas, R<1>, R denote an alkyl group (for example, methyl group, ethyl group, sulfopropyl group, etc.); R<2>-R<4> denote a hydrogen atom., alkyl group, aryl group; R2 and R3 or R3 and R4 may form a benzene nucleus. X<->, Y<-> are anion, and denote halide anion, sulfonic acid anion, perchlorate, fluoroborate, etc.; Z denotes an atom. group necessary for completing a 5- or 6-membered nitrogenous heterocycle. The more specific examples of the heterocycle include a 2-quinoline ring, 4-quinoline ring, benzothiazole, indolenine ring, etc. The low-fogging silver halide photographic emulsion for direct positives having the high sensitivity is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to a direct positive silver halide photographic emulsion. This invention relates to a positive silver halide photographic emulsion.

(B) Prior Art and Its Problems Direct positive images can be obtained using certain silver halide photographic emulsions. For example, there is a silver halide photographic emulsion comprising a capri-carrying silver halide and an electron acceptor, as described in US Pat. No. 3,501,307.

In order to increase the sensitivity of this type of silver halide photographic emulsion, selection of fogging agents and electron acceptors is important. Also used is the technique of spectral sensitization using dyes. Examples of electron acceptors used include desensitizing dyes such as pinacryptol yellow and organic desensitizers such as paraquat. However, many have low sensitivity, and
There are many that are high in Capri, but few can surpass Pinacryptol Yellow.

(C) Purpose of the Invention The present inventors have conducted intensive research to produce a direct positive silver halide photographic emulsion with high sensitivity and low fog, and as a result, have succeeded in obtaining an organic desensitizer that satisfies this purpose. did.

Therefore, an object of the present invention is to provide a direct positive silver halide photographic emulsion with high sensitivity and low fog by using a novel desensitizer as an electron acceptor.

CD) Structure of the Invention The novel organic desensitizer used in the present invention has the general formula!
and II.

■ In the formula, R' and R may be the same or different, and are an alkyl group (for example, a methyl group, an ethyl group, a sulfopropyl group, etc.)
, R2-R4 may be the same or different and represent a hydrogen atom, an alkyl group, an aryl group, R2 and R ink,
A benzene nucleus may be formed with R4 and x-, y
- is an anion, which may be the same or different, and represents a halide anion, a sulfonate anion, perchlorate, fluoroborate, etc., and 2 represents an atomic group necessary to complete a 5- or 6-membered nitrogen-containing heterocycle. represent. Specific examples of the heterocycle include 2-quinoline ring, 4-quinoline ring, benzothiazole ring, indolenine ring, benzoxazole ring, benzimidazole ring, acridine ring, imidazoquinoxaline ring, i, s-naphthyridine ring, benzo( f) There are quinoline rings, etc.

Next, typical examples of organic desensitizers used in the present invention will be given.

2H5 Ni C F1 Ni Os C2H5I- C2)iS Ni Next, a typical example of the method for synthesizing the novel organic desensitizer used in the present invention will be described. - Synthesis of Compound (1) N-ethyl-5-ethoxyquinaldinium iodide 1.75P and 3-formylpyridine 0.514Pi acetic anhydride were heated under reflux for 30 minutes.

After cooling, the crystals were collected, washed with ether, and then recrystallized from ethanol. mp234° (dec) Yield 0.
71 Synthesis of Compound (2) 3-formylpyridine 4.22 and ethyl iodide 15 were heated under reflux for 8 hours, and after cooling, the precipitated crystals were collected and washed with ether. Yield: 10.7 f m p 133-4° 3-formyl-N-ethyl-pyridinium iodide thus obtained 1. AOSR and N-ethyl-5-ethoxyquinaldinium iodide (1°71 ff) were heated under reflux for 20 minutes in anhydrous acetic acid solution.

After cooling, the precipitated crystals were collected, washed with ether, and then recrystallized from methanol. Yield 1.70Pmp 248°(d
ec) Other desensitizers used in the present invention can also be easily synthesized according to the above synthesis example.

In the present invention, an organic desensitizer can be added to the silver halide emulsion by a known method. For example, it can be added as a solution of 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.

The amount of the desensitizer used in the present invention varies depending on various factors of the silver halide photographic emulsion, but is preferably 1X10 to 2X10 mole/mole A.
g range.

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

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 gold ordnance is preferred.

The silver halide photographic emulsion D used in the present invention is
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 having a nucleus for capturing free electrons inside a silver halide crystal and whose surface is fogged with a chemical fogging agent may be used. The production of this type of emulsion can be done by e.g.
U.S. Patent No. 3,367,778, U.S. Patent No. 3,632,3
4.0 and No. 3,709,689.

The silver halide photographic emulsion used in the present invention is
Covered with chemical fogging agent. Methods of chemically imparting capri include, for example, Antoine Haute (Antoine Haute).
Sci-en Industry Photographic (Sci-en Hautot) and Henri Soupenier
ce et Industries Photogra
phique) Volume 28, pages 57-65 (published in 1957)
Favorable results are obtained using the method of chemical sensitization described in .

The silver halide photographic emulsion used in the present invention can be given capricolor by 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 fogged by 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, a silver halide photographic emulsion can be fogged by using the above method in combination with a sulfur-containing sensitizer such as sodium thiosulfate or allylthiourea, or a thiocyanic acid compound such as potassium thiocyanate.

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 resin films such as polyethylene terephthalate and cellulose acetate, synthetic paper, and waterproof paper. Also,
Paper laminated with glass can also be used. If necessary, a subbing layer can be provided on these supports using 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.

A feature of the present invention is that a novel organic desensitizer is used as an electron acceptor to obtain a direct positive silver halide photographic emulsion with high sensitivity and low capri. The present invention will be described below based on Examples, but the present invention is of course not limited thereto.

(E) Examples Examples Control A silver iodobromide emulsion (27 rutiiodine) was prepared using the control double run method. This raw emulsion had a cubic crystal habit, an average grain size of 0.25 μm, and was a monodisperse emulsion containing 95% by weight of grains within 30% of the average grain size. After washing the precipitate with water, add gelatin and adjust the pH to 8.0%.
Adjust the pAg to 5.0 and add potassium chloroaurate 2 W/m
deAg t- was added and the mixture was heated at 60° C. for 2 hours. After that, the sample valve was adjusted to pAgt'8.5 and pH 5.0, and an organic desensitizer of 200 my/mole Ag was added, a hardening agent and a surfactant were added, and the polyethylene was subbed. It was coated on a paper support laminated with a coating amount of 3.7 cm in terms of silver nitrate. After drying, each 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 using an acidic fixer. After fixing, it was washed with water and dried. As a result of concentration measurement, Table 1 was obtained.

S in the table is a value measured at an optical g degree of 0.75, and is expressed as a relative value with the value of compound A (paraquat) being 1.0. Further, Dmin represents the minimum concentration.

Compound A Br- Also, for comparison, pinacryptol yellow (compound B
) values are also shown.

Compound B λmax in the table is the absorption maximum of the desensitizer in methanol. EOX is the oxidation potential, and ER is the reduction potential, which was measured by cyclic portammetry (CV). The solvent during measurement was acetonitrile, and the supporting electrolyte was tetra n-butylammonium perchlorate (0
, 1M) was used. The concentration of the sample is 10-'M ~ 10-5
It is M. The working electrode is a stationary platinum electrode (Beckman
A39273) and the reference electrode is a saturated caramel electrode (
SCE)'i used.

(Table 1) Example 2 A silver iodobromide emulsion (
2 mol% of iodine) was prepared. This raw emulsion is a monodisperse emulsion with a cubic crystal habit and an average grain size of 0.25μ, containing grains of 95×FF1% within 30 cm of the average grain size, and after growing to 0.16μ. , potassium hexachloroiridate 50trq/mo IeAg was added, and after standing at 60°C for 20 minutes, double run was continued to grow to 0.25μ. After precipitating and washing with water, gelatin was added to adjust the pH to 6.5 and pAg to 6.
Adjusted to 2, thiourea dioxide 0.2 W/mole
Ag t'' was added and aged at 60°C for 1 hour, and 21!lV'mole Ag of potassium chloroaurate was added and incubated at 60°C for 1 hour.
5.0, divide the sample, add desensitizer to 350 zy
/mole Ag was added, and in the same manner as in Example 1,
Table 2 was obtained.

(Table 2) CF) Effects of the Invention As is clear from the examples, the organic desensitizer of the present invention has an excellent electron capture ability, and can be used as a direct positive silver halide photographic emulsion with high sensitivity and low fog. is obtained, and most of the compounds are superior to pinacryptol yellow. Furthermore, by using a sensitizing dye in combination, it is also possible to obtain a highly sensitive direct positive silver halide photographic material.

Claims (1)

[Claims] (1) A direct positive silver halide photographic emulsion containing at least one organic desensitizer represented by the general formula I or II. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ I ▲There are mathematical formulas, chemical formulas, tables, etc.▼II [In the formula, R^1 and R may be the same or different, and each represents an alkyl group. R^2 to R^4 may be the same or different and each represents a hydrogen atom, an alkyl group, or an aryl group. Also, R^
2 and R^3, or R^3 and R^4 may form a benzene nucleus. X^- and Y^- are anions and may be the same or different. Z represents an atomic group necessary to complete a 5- or 6-membered nitrogen-containing heterocycle. ]