JPS63220135A - 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 a specific cyanine dye and at least one kind of cyanopyridium salts into the emulsion. CONSTITUTION:The cyanopyridium salt expressed by formula I or II and the cyanine dye having -0.40--1.12V reduction potential and +0.85-+1.80V oxidation potential are combined. In formula, R<1>-R<8> may be the same or different, and respectively denote hydrogen, alkyl group; R<1> and R<2> or R<2> and R<3> or R<3> and R<4> or R<5> and R<6> may form a benzene ring. R denotes an alkyl group and X<-> is anion, and denotes halide ion sulfonic acid anion, perchloric acid an ion, tetrafluoroborate. The low-fogging silver halide photographic emulsion for direct positives having the high sensitivity by strong color sensitization 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, U.S. Patent No. 3,501.307
There are photographic emulsions assembled from turnip Vt-bearing silver halide and electron acceptors, as described in the patent specification.

In order to increase the sensitivity of this type of direct positive silver halide photographic emulsion, it is important to select the capacitor and electron acceptor. Spectral sensitization techniques have also been used, and many dyes have been reported.

Desensitizing dyes such as pinacryptol and organic desensitizing agents such as balacote are used as electron acceptors. By using these compounds together with cyanine dyes,
Higher sensitivity can be obtained than when using a dye alone. This phenomenon is supersensitization in direct positive emulsions.

On the other hand, when used in combination with a desensitizing dye, coloring (color staining) due to the dye remaining after the development process often occurs.・Also, baraquat tends to cause capri and has toxicity problems.

(C) Purpose of the Invention The present inventors have conducted extensive research to develop a direct positive silver halide photographic emulsion with high sensitivity and low fog, and have discovered that cyanopyridinium salts are suitable for the purpose. . 'CD) Constituent composition of the invention A cyanopyridinium salt of general formula [I] or [■] with a reduction potential of -0,40V to -1,12V and an oxidation potential of +o
By combining cyanine dyes with .

f-I][:I[] (In the formula, R-R may be the same or different, each represents hydrogen or an alkyl group, and R1 and R2 or B and R or R and B or R and R represent / May form a Zen ring,
BJ represents an alkyl group.

X- is an anion, and represents a halide ion, a sulfonate anion, a perchlorate anion, or a tetrafluoroborate. ) Next, typical examples of organic desensitizers used in the present invention will be given.

N N 2ki5 The cyanopyridinium salt used in the present invention can be easily synthesized by reaction of cyanopyridines and an alkylating agent.

Next, the details will be described using a synthesis example.

Synthesis of 2-cyano-N-ethylpyridinium iodide> 3 tons of 2-Schiff/pyridine and ethyl iodide were heated under reflux for 10 to 28 hours. After cooling, the crystals were separated several times, washed with ether, and dried. mp 168°C (dec) Yield 2.52 Synthesis of 4-cyano-N-ethylpyridinium iodide> 2t of 4-cya/pyridine and 8t of ethyl iodide were heated under reflux for 8 hours. After cooling, the precipitated crystals were collected, washed with ether, and dried.

mp 143-145° Yield 3.7F Other desensitizers used in the present invention can also be easily synthesized according to the above example.

The sensitizing dye used in the present invention has a reduction potential CBR) car 0
．． 40V~-1,12V f oxidation potential (Box) 10
．． 86V to +1.80V. Although the redox potential can be measured using polarography, we used cyclic portammetry, which is easy to record and has good reproducibility. The measurement solvent was acetonitrile, and the supporting electrolyte was tetra-n-butylammonium perchlorate (0,1
M)'i used. The 0 degree of the sample is 10-10 M, and the reference electrode is SCE.

A stationary platinum electrode was used as the working electrode.

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

The absorption maximum value (nm) and redox potential of the methanol solution of the representative example of the dye used in the present invention are as follows.

Dye λmax EHBox (1)
525 -1.12 +0.86(2)
485 -1.10 +1.28(3)
504 -0.78 +1.41(
4) 432 -0.78 +1.7
2(5) 519 -0.73 -1-
1.49 (6) 443 -0.58
+1.80 471 -0.40
+1.70 (8) 505 -0.46
+1.69 (9) 495 -1
．． 08 +1.20 (10) 460
-0.96 +1.15 (11) 48
0 -0.84 +1.42(12)
508 -0.82 +1.41(13
) 519 -0.64 +1.55
In the present invention, a dye and a 3-cyanopyridinium salt can be added to a silver halide photographic emulsion by a known method. For example, methanol, ethanol, panol, pyridine, dimethylformamide, acetone,
It can be added as a solution in a single or mixed solvent such as water.

It can also be added to the emulsion using ultrasonic dispersion. Additionally, methods known 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
05, and the method described in the same specification No. 2,912,3.43 can also be used.

The amount of the dye and cyanopyridinium salt used in the present invention varies depending on various factors of the silver halide photographic emulsion, but is preferably 1 x 10-5 to 2 x 1
0 mole/mole Ag (D 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.

Further, the dye and the cyanopyridinium salt may be added at the same time or whichever comes first.

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 this type of emulsion can be done by e.g.
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 for chemically imparting capri include, for example, AndOne Auto (An
Sci-e Industry Photographic (Sci-e Hautot) and Henri 5aubenier
nce et Industries Photogr.
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 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 be fogged by combining a reducing agent with a metal compound having a JA potential as well as silver. Specific examples of metal compounds having a potential more noble than silver potential include, in addition to the gold compounds mentioned above, platinum compounds such as potassium chloroplatinate, and iridium compounds such as potassium hexachloroiridate.

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 mark-retaining 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, cellulose ether, and the like.

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. It is also possible to use paper laminated with plastic. If necessary, a subbing layer can be provided on these supports by a known method.

The invention! A photosensitive material coated with an m-positive silver halide photographic emulsion is processed in a known processing bath for development, fixing, bleaching, etc., or a processing bath in combination thereof.

The feature of the present invention is that the reduction potential is -0,40V to -1,12V.
The R potential is +0.85V ~ +1.80VO)','
By using a 727 dye and a cyanopyridinium salt in combination, a direct positive silver halide photographic emulsion with high sensitivity and a low capri level 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 Control A silver iodobromide emulsion (27 ruti-iodine) was prepared using the control double run method. This raw emulsion was a monodispersed emulsion with a cubic crystal habit, an average grain size of 0.25 μm, and 95 mft% of grains within 30% of the average grain size. After washing the precipitate with water, add gelatin and adjust the pH to 8.0.
% pAg was adjusted to 5.0, potassium chloroaurate, A2
r4/mde Ag'e was added and the mixture was covered at 60°C for 2 hours. After that, adjust the pAg 'i to 8.5 and pH to 5.0, divide the sample valve, and add the dye to 350η/mol e.
Ag e was added. Furthermore, cyanopyridinium salt 2001
9/mole Ag was added, a hardening agent and a surfactant were added, and the coating was applied to a paper support laminated with subbed polyethylene at a coating weight of 3.7 fβ in terms of silver nitrate. Each sample after drying? :Cut to appropriate size 0.15
The film was exposed to light through a wedge having a density difference of , and then developed at 20° C. for 90 seconds using Kodak's D-72 developer, fixed using an acidic fixer, washed with water, and dried.

As a result of humidity measurement, Table 1 was obtained.

S in the table is a value measured by a ζ-rotometer with an optical density of 0.75, and is expressed as a relative value, with the case of the dye alone being 100. Dmin is the minimum concentration. The structure, absorption maximum (nm), and redox potential (V) of the cyanopyridinium salt used and the dye (A) for comparison are as follows.

Dye (A) Compound B Compound C CoC2H5 Compound D (para;-t) Br- Table 1 As is clear from Table 1, the cyanopyridinium salt of the present invention has a reduction potential of -0,40V to -1,12V. When used in combination with a cyanine dye having an oxidation potential of +0.85 V to +1.80 V, supersensitization is observed and the capri level is low.

(F) Effects of the Invention The present invention is characterized in that a cyanopyridinium salt is used as an electron acceptor, and a direct positive silver halide photographic light-sensitive material with high sensitivity and low capri can be obtained by supersensitization. be.

Claims (1)

[Claims] The reduction potential is -0.40V to -1.12V and the oxidation potential is +
Cyanine dye of 0.85V to +1.80V and general formula [
At least one of the cyanopyridinium salts of [I] or [II]
A direct positive silver halide photographic emulsion characterized by containing seeds. ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I]▲There are mathematical formulas, chemical formulas, tables, etc.▼[II] [In the formula, R^1 to R^8 may be the same or different, and each represents hydrogen, an alkyl group, indicates R^1 and R^2 or R
A benzene nucleus may be formed by ^2 and R^3, R^3 and R^4, or R^5 and R^6. R represents an alkyl group. X^- represents an anion. ]