DD281264A5 - PROCESS FOR THE CHEMICAL SENSITIZATION OF PHOTOGRAPHIC SILVER HALOGENIDE EMULSIONS - Google Patents

Abstract

The invention relates to a process for the preparation of photographic silver halide emulsions and has the object of effecting, by the use of sulfur-containing salts, an improved sensitization, clarification and stabilization of such emulsions. The object is achieved by providing the photographic emulsion with at least one salt of the general formula {recording method; chemical sensitization; Photograph; Emulsion; Clear holder; Thiooxalsaeure; Emulsion stabilizing}

Description

Field of application of the invention

The invention relates to a process for the chemical sensitization, clarification and stabilization of photographic silver halide emulsions used for the production of photographic recording materials.

Characteristic of the known state of the art

Already described is the effect of sulfur sensitizers to increase sensitivity, clarity and stability improvement in BE-PS 616213 and FR-PS 14619671.

The sulfur-containing compounds with simultaneous use of gold compounds, HAuCI ₄ , AuCI ₃ (DE-AS 1185481, DE-PS 1174156), KAu (SCN) ₂ , KAuCI ₄ (US-PS 3320069), reducing agents in an amount corresponding to a concentration from 15 mg to 330 mg SO ₂ per kg gelatin (GB-PS 727982, ÜS-PS 2983609, US-PS 2604397, DE-PS 1174156, DE-PS 1175073), other polyvalent metal ions (DD-PS 215409, DD PS 215410) and noble metal compounds (DD-PS 231430 A1, DD-PS 237230 A1, DD-PS 244644 A1, DE-PS 964561, US-PS 2540086) are used. A disadvantage of known methods of emulsion preparation is that most of the sensitisers used produce higher sensitivity coupled with an increase in fog. The reason for this is the high amount of labile sulfur in these compounds, which is necessary because these sulfur sensitizers produce sensitivity and fogging germs alike.

The use of a smaller amount of sensitizer would result in less fog, but also a lower sensitivity gain.

The chemical sensitizing effect of salts of thiooxalic acids and their antifogging power and their influence on the stability improvement of photographic emulsions are unknown and unexpected.

Object of the invention

The object of the invention is to provide a process for improved chemical sensitization, clarification and stabilization of photographic silver halide emulsions.

Explanation of the essence of the invention

The object of the invention is therefore to find chemical compounds which cause an increase in sensitivity with only a slight haze for the chemical sensitization, clarification and stabilization of photographic silver halide emulsions which are used to prepare photographic recording materials. The object is achieved in that the photographic silver halide emulsion, a sulfur-containing salt of the general formula

A ₂ X,

in which A = ion of the I. main group of the PSE or R ₄ E ⁺ with R = H, alkyl or aryl, E = element of the main group of the PSe and X = dianion one of the thiooxalic acids, added.

Use of these compounds in photographic silver halide emulsions causes an increase in low fog sensitivity.

The compounds used are readily soluble in water or in water-immiscible solvents and sufficiently stable in solution.

Completely surprising here is the effect of the claimed compounds as chemical sensitizers and as clear coaters and stabilizers. The compounds may be added with advantage in a process step of chemical ripening, the physical ripening or the Begußin a concentration of 1.2 x 10 ^-7 to 5.0 x 10 ^-3 mol / mol of silver of the emulsion.

The compounds according to the invention with other chemical sensitizers, such as. As gold (III) chloride, potassium di (thiocyanato) aurate (l) or tetrachloroauric acid and salts thereof in concentrations of 10 " ⁷ to 1.5 χ 10 ~ ³ MoIdOId per mole of silver, can be used with precious metal compounds and reducing agents.

The compounds may according to the invention all emulsion types, such as. Silver bromide emulsions, silver chloride emulsions, silver bromide emulsions, silver chlorobromide emulsions, silver bromide iodide emulsions, silver iodobromide emulsions, silver chlorobromide iodide emulsions.

The emulsions composed in this way can be prepared both by single-jet and by double-jet emulsification.

Both boiling emulsions and emulsions, which in the presence of Silberhalogenidlösungsmitteln, such as. As ammonia, thioether, cysteine, bromide excess or rhodanide can be prepared can be used.

The grain size distribution of the crystals can be monodisperse, narrowly distributed and widely distributed.

The emulsions may contain silver halide crystals having an average grain diameter of 0.01 m to 5.0 m, the crystals being cube-shaped with / 100 / faces, octahedral with / 111 / faces, both with / 100 / and with / 111 / Surfaces and with a spherical habit.

According to the invention, the emulsion may also contain other photographic additives such as clear coaters, stabilizers, spectral sensitizers, curing agents, couplers and wetting agents, among others. be added.

The emulsions prepared according to the invention are suitable for the preparation of black and white photographic and color recording materials.

They can be developed with equally good results at processing temperatures of 15 to 45 ° C.

embodiments

A selection of the tested connections is shown below:

(PImAs) 2

^N 0

(Et

(Fh - CH2 - PPh3) 2

Кг '

"/ ·%

Example 1:

For testing, a silver bromide iodide-ammonia emulsion, prepared by the single-jet process, with a logarithmic normal distribution of Ig = 0.12 and an average grain diameter of 1.2 m was used. The emulsion having a iodide content of 4.5 mol% has a silver gelatin ratio of Ag: gelatin = 3.0 and a silver halide concentration of 2 mol AgX / kg emulsion.

The chemical maturity is carried out at 50 ⁰ C and after 90 minutes with 2x 10 ~ ³ mol 5-methyl-7-hydroxy-1,3,3, a, 7-tetraazaindene (TAI) terminated. Thereafter, the samples are diluted with five times the amount of gelatin solution (8-Ma .-%) and poured onto glass plates. After drying and cutting, the samples are exposed through a step wedge with a step difference in density D = 0.15 in a Kugelsensitometer 0.04s with incandescent light and developed for 5 minutes at 20 ⁰ C in a developer of the following composition:

Monomethyl-p-aminophenol 1.5g sodium 18.0 g hydroquinone 2.5 g potash 18.0 g Wasserauf Fill 1 000 ml

Each unexposed strip is developed for 20 minutes. After a short intermediate watering in

Acetic acid solution 0.2%

is fixed in a fixer of the following composition for 5 minutes at 20 ⁰ C:

Sodium thiosulfate 5-hydrate 200 g called potassium 20 g Water on Fill 1 000 ml

Thereafter, the samples are watered as usual, dried and measured on the densitometer.

The test substance is added to the photographic emulsion at the beginning of the chemical ripening as an acetone solution.

Table 1 summarizes the results with substance 2:

table 1 Compound concentration mol / mol AgX ds D ₂₀ Exposure 0.04 s; D = 0.15 5 'development Eo.s gN sample NJ NJ NJ Ol NJ о ui X X I I t σι Si 0.05 0.18 0.42 0.24 0.36 0.87 eo ,, 0.11 7.0 0.24 27.0 0.85 A B C - Minimum density evolution 5 '- Minimum density evolution 20' - relative sensitivity E ₀ , i = f (D _min + 0.1) - relative sensitivity E ₀ , 5 = f (D _min + 0.5) gradation 11.0 23.5 34.0 D ₅ D ₂₀ Eo ,, Eo.5 - gN

The results show a significant increase in sensitivity after addition of the test substance.

Example 2

The emulsion samples are prepared according to Example 1 and matured according to the invention with the appropriate compounds, the process being extended to the chemical maturity by the additional addition of a solution consisting of a mixture of Tetrachlorogoldsäure'und Ammoniumrhodanid

 Table 2 shows the results:

Table 2

Exposure 0.04s; D = 0.15; 5'-exposure

attempt Concentration mol / mol Ag substance 2 HAuCl ₄ NH ₄ SCN D ₅ D ₂₀ eo ,, Eo, 5 gN C D 5,0x10 ~ ⁶ 5,0 χ 10 "° 2,3xiO ~ ^e 1.5 χ 10 " ⁴ 0.42 0.17 0.87 0.34 34.0 36.5 27.0 31.0 0.85 1.2

Very clearly, Table 2 shows that the addition of HAuCl ₄ and NH ₄ SCN results in an increase in sensitivity associated with fog reduction and gradation enhancement.

Claims (3)

1. A process for the chemical sensitization of photographic silver halide emulsions, characterized in that the emulsion in addition to conventional additives at least one ionic compound of the general formula A ₂ X, in the A = lon of the I. main group of the PSE or R ₄ E ⁺ with R = H, alkyl or aryl radical E = element of V. Main group of the PSE and
X = dianion of one of thiooxalic acids
mean, in an amount of 1.2 x 10 ^-7 bis5,0x 10 ^-3 mol / mol of silver is added. 2. A process for the chemical sensitization of photographic silver halide emulsions according to claim 1, characterized in that the emulsion additionally further additives, such as. B. adds gold and sulfur compounds. 3. The method for chemical sensitization of photographic silver halide emulsions according to claim 1 and 2, characterized in that the additions of A ₂ X are added to the emulsion in a process step of chemical ripeness, physical ripeness and pouring, respectively.