DE19525036A1 - Process for digestion of silver halide emulsions - replacing sulphur cpds. with seleno-organic cpd. to enhance sensitivity while maintaining low fogging and grain - Google Patents

Abstract

A process for digestion of silver halide emulsions at 35-65[deg]C and pH 2-10 utilises 10-9 to 10-3 moles per mole of silver halide of formula (I); Y = C=X, C-Z or SO2; X = O or NR2; Z = halogen; n = 0, or 1 in case of Y = C-Z; R1 = H or substit. or forming fused ring with X; R2 = H or substit.; and Q = atoms to form a 5- or 6-membered ring.

Description

The invention relates to a method for the chemical ripening of silver halide emulsions.

The ripening of silver halide emulsions (Ullmann’s Encyclopedia of Industrial Chemistry, Vol. A 20 (1992), p. 36 ff) serves to increase the sensitivity of the light To increase silver halide emulsions without increasing the fog.

A large number of compounds and methods have already been proposed how and how this ripening should be carried out.

The best known ripening agents are gold and sulfur compounds, e.g. B. sodium thiosulfate as a sulfur compound. To the sensitivity achieved further It has recently been proposed to increase the sulfur compounds to be replaced in whole or in part by selenium compounds.

The increase in sensitivity achieved with the known selenium ripening agents is for a number of purposes are still insufficient. In particular, many of the known selenium ripeners from a veil rise, which for a number of Products, e.g. B. for the films of so-called disposable cameras in which high Sensitivity, low graininess and low haze are required is unacceptable.

The object of the invention was to overcome these disadvantages.

It has now surprisingly been found that this can be achieved using a method for ripening silver halide emulsions in which the silver halide is treated at 10 to ⁹ to 10 ^-3 mol of a compound of the formula I / mol of silver halide at 35 to 65 ° C. and pH 2 to 10 becomes:

wherein
YC = X, C⊕-Z or SO₂,
XO or NR₂,
Z halogen, especially chlorine,
An⊖ an anion, especially chloride,
n O or, if YC⊕-Z means 1,
R₁ is hydrogen or a substituent or together with X the remaining members of a fused ring,
R₂ is hydrogen or a substituent and
Q represents the atoms required to complete a 5- or 6-membered ring.

As substituents R₁ and R₂ come in particular alkyl, aryl, acyl and heterocyclic groups in question, which in turn can be further substituted.

Preferred compounds correspond to formulas (II) and (III):

wherein R₁ has the meaning given above.  

Preferred radicals R₁ are phenyl, C₁-C₄-alkyl, benzyl and cyclohexyl, wherein Phenyl may be further substituted by C₁-C₄ alkyl.

Suitable compounds of formula (I) with Y = CO and Q = C₆H₄ (formula III) are:

Other suitable compounds of the formulas (I) are:

The silver halide emulsion preferably consists of AgBrI or AgBrICl crystal len with up to 15 mol% iodide and up to 20 mol% chloride or from AgClBrI, AgClI or AgClBr crystals with at least 50 mol% chloride.

The chemical ripening is especially at pAg values between 6.5 and 9.0 carried out. The ripening time is preferably 80 to 120 minutes.

In a preferred embodiment, chemical ripening takes place with a Combination of labile sulfur compound and one of the compounds of the Formula (I).

Chemical ripening at pH values between 4 and 8 is preferred guided.

The emulsion preferably consists of at least 50% of the projected area from tabular grains with an aspect ratio of at least 2.

In a further preferred embodiment, the emulsion consists of one Share of at least 50% from hexagonal tabular grains, Emul are particularly preferred, the proportion of hexagonal tabular Grains is at least 70% and their neighboring edge ratio is between 2: 1 up to 1: 1.

Emulsions whose crystals have a narrow grain size are also preferred have distribution.

The distribution width V of an emulsion is defined as

V is preferably 25%, in particular 20%.

example 1 Emulsion Em-1

A solution of 345 g of inert gelatin, 1.2 g of potassium was added to the batch kettle bromide and 104 ml of l-methylimidazole in 9.75 kg of water with stirring. At 40 ° C the pH was adjusted to 6.3 and then an aqueous silver nitrate solution (255 g silver nitrate in 3 kg water) and an aqueous halide solution (180 g potassium bromide in 3 kg water) as a controlled double inlet within 10 minutes at 63 ° C and a pBr of 2.85 metered. A second followed Controlled double entry of an aqueous silver nitrate solution (128 g silver nitrate in 350 g water) and an aqueous halide solution (90 g potassium bromide in 350 g Water) within 12 minutes at 63 ° C and a pBr of 2.85. Im at closing controlled double inlet was an aqueous silver nitrate solution (2 166 g silver nitrate in 6 kg water) and an aqueous halide solution (1 545 g Potassium bromide in 6 kg water) within 110 minutes at 63 ° C and one pBr of 1.83 metered in. After the last run-in, the emulsion was brought up to 23 ° C cooled, flocculated at pH 3.5 by adding polystyrene sulfonic acid and then washed at 20 ° C. The flocculate was then rinsed with water 7.5 kg filled and by adding 930 g of inert gelatin and 2.5 kg of water pH 6.5 and a temperature of 50 ° C redispersed. The volume focus the octahedral AgBr emulsion was 0.53 µm and the distribution width was 20%.

The emulsion Em-1 was at 50 ° C, a pH of 6.0 and a pAg of 8.0 with 14 µmol ripening agent / mol Ag according to Table 1, 3.1 µmol tetrachlorogold acid / mol Ag and 410 µmol potassium thiocyanate / mol Ag chemically matured.

After cooling to 40 ° C., addition of 4.0 mmol of 4-hydroxy-6-methyl-1,3,3a, 7- tetraazaindene per mole Ag and 80 µmol 1-phenyl-5-mercaptotetrazole per mole Ag the ripened emulsions were on a cellulose acetate film of 120 microns thick shed with an order of 6 g / m² (based on AgNO₃).

The cured and dried film samples were graduated behind a Gray wedge exposed to daylight and processed in a black and white process:  

The sensitivity data refer to a density of 0.2 over fog. Relative values are given, with sensitivity and fog the emulsion ripened with thiosulfate was set at 100.

Table 1

As can be clearly seen from Table 1, one obtains with the invention according to selenium compounds a higher sensitivity with the same to better Veil.

Example 2 Emulsion Em-2

An aqueous silver nitrate solution (170 g of silver nitrate in 400 g of water) and an aqueous halide solution (73 g of sodium chloride and 1.2 g of potassium bromide in 400 g of water) were simultaneously taken at 50 ° C. over a period of 120 minutes at a pAg of 7.7 vigorous stirring to a solution of 30 g of gelatin in 400 g of water. An AgCl _0.005 Br _0.005 emulsion with an average particle diameter of 0.8 μm was obtained. The emulsion was flocked in a known manner, washed and redispersed with the addition of gelatin, so that the gelatin / AgNO₃ ratio was finally 1.0.

The emulsion Em-2 was at 47 ° C, a pH of 5.0 and a pAg of 7.3 with 1.5 µmol tetrachloroauric acid / mol Ag, 20 µmol potassium thiocyanate / mol Ag and 15 µmol ripening agent / mol Ag chemically ripened according to Table 2.

After cooling to 40 ° C, the emulsion with 380 µmol S-1 / mol Ag for the blue spectral range sensitized and with 250 µmol 1-phenyl-5-mercaptotetra zol / mol Ag stabilized. Then the emulsion described above with an emulsifier of the yellow coupler Y-1 and the white coupler W-1 in tricresyl added to phosphate and on a layer support made of polyethylene on both sides coated paper.

The layer contained per m²:
0.75 g emulsion (based on AgNO₃)
1.38 g gelatin
0.95 g yellow coupler Y-1
0.2 g white coupler W-1
0.29 g tricresyl phosphate

A protective layer of 0.2 g gelatin and 0.3 g hardness was applied over this layer poured H-1 per m². The material was exposed imagewise and processed according to the Ektacolor RA4 process. The sensitivity details relate density of 0.2 over veil. Relative values are displayed give, with the sensitivity and the haze of only ripened with thiosulfate Emulsion was set to 100 each.

Emulsion Em-3

Emulsion Em-3 was prepared and processed like Em-2, but with the change that the aqueous halide solution had the following composition:
73 g sodium chloride, 1.2 g potassium bromide, 0.034 mg dipotassium hexachloroiridate (IV), 0.010 mg rhodium trichloride and 0.060 mg hexachloroauric acid in 400 g water.

Emulsion Em-4

• a) Preparation of the pre-precipitation
  A solution of 110 g of inert gelatin in 7 kg of water was placed in the batch kettle with stirring. At 40 ° C., an aqueous silver nitrate solution (36 g silver nitrate in 400 g water) and an aqueous halide solution (26 g potassium bromide in 400 g water) were metered in as a double inlet within 2 minutes. This was followed by the addition of 220 g of inert gelatin in 880 g of water. After heating to 60 ° C., an aqueous silver nitrate solution (89 g of silver nitrate in 300 g of water) was added in the course of 4 minutes in order to establish a pBr value of 2.0 in the dispersion medium. Then the temperature was raised to 65 ° C and the second double inlet followed. An aqueous silver nitrate solution (150 g silver nitrate in 900 g water) and an aqueous halide solution (35 g potassium iodide and 64 g potassium bromide in 900 g water) were metered in over the course of 8 minutes. During the run-in, the pBr value in the dispersion medium was kept constant at the initial value of 2.0. The emulsion was cooled to 25 ° C, flocculated at pH 3.5 by adding PSS and then washed at 20 ° C. The flocculate was then made up to 11.5 kg with water and redispersed at pH 6.5 and a temperature of 50.degree.
• b) Preparation of the tabular grain emulsion:
  The entire pre-precipitation was melted and digested at 65 ° C. After the pBr value had been set to 1.7 in the dispersion medium with aqueous 2N KBr solution, an aqueous silver nitrate solution (1,020 g silver nitrate in 2.5 kg water) and an aqueous halide solution (607 g potassium bromide in 2.5 kg water) added. The pBr value in the dispersion medium was kept constant at the initial value of 1.7.
  After the last run-in, the emulsion was cooled to 25 ° C. and flocculated at pH 3.5 by adding polystyrene sulfonic acid and then washed at 20 ° C. The flocculate was then redispersed by adding 59 g of inert gelatin in 2.6 kg of water at pH 6.5 and a temperature of 50.degree. The AgBrI emulsion consisted of over 80%, based on the projection area of the crystals, of hexagonal tabular grains with an aspect ratio between 1.0 and 1.5. The volume focus was 0.44 µm, the distribution width 19% and the iodide content 2.8%.

The emulsion Em-4 was spectrally sensitive at 40 ° C with 600 µmol S-2 / mol Ag siert and then at 55 ° C, a pH of 6.0 and a pAg of 7.5 with 21 µmol ripening agent / mol Ag according to Table 2, 5.0 µmol tetrachloroauric acid / mol Ag and 690 µmol potassium thiocyanate / mol Ag chemically ripened.

The samples were mixed with an emulsifier of the cyan coupler C-1, 4 mmol ⁴-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene per mol Ag and 80 µmol 1-phenyl-5-mercaptotetrazole per mol Ag on a Cast cellulose acetate film of 120 µm thickness with the following application quantities per m²:
4.0 g emulsion (based on AgNO₃)
3.0 g gelatin
0.80 g cyan coupler C-1

The cured and dried film samples were graduated behind a Gray wedge exposed to daylight. After that, the materials according to the in British J. of Photography 1974, p. 597 processed process. The Sensitivity data refer to a density of 0.2 over fog. It  relative values are given, the sensitivity and the haze of the only with emulsion ripened with thiosulfate was set to 100.

Table 2

It can be seen from Table 2 that with the ripening agents according to the invention Sensitivity / fog ratio can be significantly improved. Especially the advantages of tabular grain emulsions are pronounced.  

Substances used in the examples:

Claims (6)

1. A process for the ripening of silver halide emulsions, characterized in that the silver halide is treated at 35 to 65 ° C and pH 2 to 10 with 10 ^-9 to 10 ^-3 mol of a compound of formula I / mol of silver halide: wherein
YC = X, C⊕-Z or SO₂,
XO or NR _2,
Z halogen,
An⊖ an anion,
n O or, if YC⊕-Z means 1,
R₁ is hydrogen or a substituent or together with X the remaining members of a fused ring,
R₂ is hydrogen or a substituent and
Q are the atoms required to complete a 5- or 6-membered ring. 2. The method according to claim 1, characterized in that the compound of formula I corresponds to formula III wherein R₁ has the meaning given in claim 1. 3. The method according to claim 1, characterized in that the compound of formula I corresponds to formula II wherein R₁ has the meaning given in claim 1. 4. The method according to claim 1, characterized in that the Silver halide emulsion made of AgBrI or AgBrICl crystals with up to 15 mol% iodide and up to 20 mol% chloride. 5. The method according to claim 1, characterized in that the Silver halide emulsion made of AgClBrI, AgClI or AgClBr crystals there is at least 50 mol% of chloride. 6. The method according to claim 1, characterized in that the Silver halide emulsion to at least 50% of the projected area tabular grains with an aspect ratio of at least 2 consists.