DE19533687A1 - Chemical sensitisation of silver halide emulsion to optimise speed fog ratio, esp. at sensitivity max. - Google Patents

Abstract

In chemical sensitisation of Ag halide (AgX) emulsions with (a) Au and (b) S or Se cpds. in the presence of spectral sensitisers, < 10 wt.% of the optimum amt. of dye for sensitivity and 10<-6> to 10<-3> mole cpds. of formulae (I) to (IV)/mole AgX are added before or during addn. of the chemical sensitisers but after coagulation; in which X = O or S; R1 = H, Cl or 1-4 C alkyl; X = O or S; R1 = H, Cl or 1-4 C alkyl; R2 = H, -CO-, -COOR6 or -SO2-R6; R3, R4, R5 = opt. substd. alkyl; R6 = 1-4 C alkyl or phenyl; m = 5-12; n = 1-4; o = 1-3.

Description

The invention relates to a method for the chemical ripening of silver halide emulsions with gold and sulfur or selenium compounds in the presence of spectral sensitizers that increase sensitivity in the area spectral sensitization, to an improved blue-minus blue distance and leads to a sensitivity fog optimization.

State of the art

Photographic silver halide gelatin emulsions are for ultraviolet and only blue light sensitive. They can be treated with suitable sensitizer dyes but for light of the entire visible spectral range and for infrared rays sensitize spectrally. Suitable sensitizer dyes must be added to the Surfaces of the silver halide microcrystals of the photographic emulsions easily be absorbable and also have the ability to absorb the energy of to transfer the absorbed photons to the silver halide microcrystals, where it eventually leads to the formation of the latent image.

For the production of chemically and spectrally sensitized photographic silver Halide gelatin emulsions have the following four process steps a) to d) enforced self-contained procedure. These are

• a) the precipitation of highly disperse, colloid-protected, almost un in water soluble silver halides by double reaction between aqueous Alkali or ammonium halide solutions and aqueous silver or sil berdiamine nitrate solutions in the presence of gelatin as a protective colloid, with the precipitation in order to bring about desired dispersities can follow a so-called physical maturation,
• b) the removal of the solution during precipitation and physical ripening remaining agents, such as nitrate ions, alkali ions, ammonium ions after the so-called flock washing process, after the pasta washing process drive or by ultrafiltration;  
• c) post-ripening, also called chemical ripening, in the course of which the chemical sensitization of the emulsions takes place by means of sulfur or selenium compounds, rhodanoaurates (I), rhodano pallate (II) added in trace amounts. For this, the emulsion is 30 to 360 min. long digested at 36 ° C to 60 ° C. In the course of this digestion, the light sensitivity of the emulsions increases significantly. The veil remains almost constantly low until it reaches maximum sensitivity, but then rises more or less. The chemical ripening must therefore be stopped immediately after reaching the point in time, t _opt , that is the point in time at which the optimal sensitometric parameters of the emulsions have been reached. The chemical ripening is stopped by cooling the emulsion and, if appropriate, by adding stabilizers. Stabilized emulsions are stored for a few days to weeks in cold rooms for their further processing to form the light-sensitive layers of the photographic image recording materials. In the course of this operation, ripening centers have formed on the silver halide microcrystals, which, depending on their dispersity in particular, can preferably serve as electron donors or electron acceptors in the processes which take place between light absorption and the development of latent image nuclei;
• d) Addition of sensitizer dyes to those previously remelted and for the basting to light-sensitive image recording materials conditioned chemically ripened emulsions. This will make the chemically ripened emulsions also for light of those wavelengths sensitized by the introduced sensitizer dyes be absorbed. The efficiency of this spectral sensitization depends now decisively depend on the fact that as many light-excited as possible Dye molecules can be reduced and the resulting Dye radicals lose their excess electrons with as little loss as possible able to implement developable latent image germs.

It is advantageous to use the sensitizing dyes before or during the process mix ripening (US 5 075 209) or before chemical ripening together with Add potassium iodide (JP 02/068540). Another advantage is the sensitivity Coloring dyes before chemical ripening in the presence of solvents  add (EP 460 800). Finally, DD 2 98 696 describes the addition of only one Part of the sensitizing dye before or during chemical ripening. According to EP 566 075 5-bromo-7-hydroxy-1,2,3-triazolo [1,5-a] pyrimidine in the chemical ripening used together with spectral sensitizers.

The object of the invention was the sensitivity thus achieved and in particular the To further increase the sensitivity / fog distance.

This is achieved in that before or during the addition of the ripening substances, but after the precipitation, at least 10% by weight of the amount of dye which is optimal for the sensitivity and between 10 ^-6 and 10 ^-3 mol of compounds of the formulas I to IV each Mol of silver halide can be used. The amount of dye required for optimal sensitivities is added minus the amount added before or during chemical ripening after chemical sensitization.

In particular, 10 to 95% by weight are used before or during chemical ripening added to the amount of sensitizing dye.

Sensitizing dyes are preferred whose oxidation potential is between +1.8 and +0.5 V, preferably between +1.6 and +0.7 V and their Excitation energies 1.7 to 2.7 eV, preferably 1.9 to 2.6 eV.

Mean in the formulas
X 0 or S,
R₁ H, Cl or C₁-C₄ alkyl,
R₂ H, -CO-, -COOR₆ or -SO₂-R₆,
R₃, R₄, R₅ independently of one another unsubstituted or substituted alkyl,
R₆ C₁-C₄ alkyl or phenyl,
m 5 to 12,
n 1 to 4,
o 1 to 3,
Alkyl R₃, R₄, R₅ is in particular C₁ to C₄ alkyl.

In a preferred embodiment, the emulsion before or during the chemical ripening added polyvalent metal ions, in particular special compounds of the following metals come into consideration.

Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cd, Sn, Ba, Ce, Eu, W, Re, Os, Ir, Pt, Hg, TI, Pb.

Mixtures of two or more polyvalent metals can also be used. The following metals are particularly suitable:
Mg, Ca, Mn, Fe, Ni, Cu, Zn, Cd, Pb, Ir, Pd and Pt.

The metal compounds are used in particular in an amount of 10 ^-8 to 10 ^-1 mol / mol silver halide, preferably 10 ^-6 to 10 ^-5 mol / mol silver halide.

The ripening process according to the invention is particularly in the case of silver bromide iodide sions successful, preferably in those whose silver iodide content 5 to Is 15 mol%.

The mean diameter of the equal-volume sphere of the emulsion grains is preferably 0.3 to 2.0 µm, in particular 0.5 to 1.5 µm.

Silver halide emulsions in which hexagonal tabular ones are preferred Grains (tab-grains) from at least 50% of the projected area of the emulsion make, especially those where the neighboring edge ratio of the hexago nale boards between 2: 1 and 1: 1 and especially those whose aspect ratio is 5: 1 to 20: 1, the aspect ratio being the ratio of Diameter of the circle with the same area as the projection surface to the thickness of the Is tab-grains.

The proportion of tab-grains is in particular 70% of the projected area of the Emulsion.

The emulsions can additionally be doped with metal compounds, i. H. in Presence of metal compounds. Are preferred for the Doping compounds of iridium, rhodium, gold, osmium, palladium or platinum.

For spectral sensitization, all common sensitizers are particularly important dyes suitable, each based on the absorption maximum that they Give silver halide grain, be selected and have an oxidation potential indicate that is in the above range.

The well-known gold, sulfur and selenium compounds are used as ripening substances gene used.  

The silver halide emulsions ripened according to the invention are suitable for all photosensitive silver halide materials, but especially for color photos graphic recording materials.

Examples of color photographic materials are color negative films, color reversal films, color positive films, color photographic paper, color reversal photographic paper, color sensitive materials for the color diffusion transfer process or the sil over color bleaching process.

The photographic materials consist of a support on which at least one photosensitive silver halide emulsion layer is applied. As a carrier thin films and foils are particularly suitable. An overview of carriers materials and auxiliary layers applied to their front and back are in Research Disclosure 37254, Part 1 (1995), p. 285.

The color photographic materials usually contain at least one red sensitive, green-sensitive and blue-sensitive silver halide emulsions layer and, if necessary, intermediate layers and protective layers.

Depending on the type of photographic material, these layers can be arranged differently. This is shown for the most important products:
Color photographic films such as color negative films and color reversal films have 2 or 3 red-sensitive, cyan-coupling silver halide emulsion layers, 2 or 3 green-sensitive, purple-coupling silver halide emulsion layers and 2 or 3 blue-sensitive, yellow-coupling silver halide emulsion layers on the support in the order given below. The layers of the same spectral sensitivity differ in their photographic sensitivity, the less sensitive sub-layers generally being closer to the support than the more sensitive sub-layers.

Between the green sensitive and blue sensitive layers is more common a yellow filter layer, which prevents blue light from entering the to get layers below.

Color photographic paper, which is usually much less sensitive to light as a color photographic film, points in the order given below  usually a blue-sensitive, yellow-coupling silver halo on the carrier genide emulsion layer, a green-sensitive, purple-coupling silver halide emulsion layer and a red-sensitive, cyan-coupling silver halide emulsion layer on; the yellow filter layer can be omitted.

Deviations in the number and arrangement of the photosensitive layers can occur to achieve certain results. For example, you can all highly sensitive layers in one layer package and all low sensitivity layers to another layer package in a photographic film be summarized to increase the sensitivity (DE 25 30 645).

The possibilities of the different layer arrangements and their out effects on the photographic properties are described in J. Int. Rec. Mats., 1994, Vol. 22, pages 183-193.

Essential components of the photographic emulsion layers are binders, Silver halide grains and color couplers.

Information on suitable binders can be found in Research Disclosure 37254, Part 2 (1995), p. 286.

Information about suitable silver halide emulsions, their preparation, maturation, Stabilization and spectral sensitization including suitable spectrals sensitizers can be found in Research Disclosure 37254, Part 3 (1995), pp. 286 and in Research Disclosure 37038, Part XV (1995), p. 89.

Photographic materials with camera sensitivity usually contain Sil berbromide iodide emulsions, which may also contain small amounts of silver chloride can contain. Photographic copying materials contain either silver chloride bromide emulsions with up to 80 mol% AgBr or silver chloride bromide emulsions with over 95 mol% AgCl.

Information on the color couplers can be found in Research Disclosure 37254, Part 4 (1995), p. 288 and in Research Disclosure 37038, Part II (1995), p. 80. The maximum absorption of the dyes formed from the couplers and the color developer oxidation product is preferably in the following areas:
Yellow couplers 430 to 460 nm, purple couplers 540 to 560 nm, cyan couplers 630 to 700 nm.

In color photography films, to improve sensitivity, Graininess, sharpness and color separation are often used in compounds Reaction with the developer oxidation product release compounds, the photo are graphically effective, e.g. B. DIR couplers that have a development inhibitor columns.

Information on such connections, in particular couplers, can be found in Research Disclosure 37254, Part 5 (1995), p. 290 and in Research Disclosure 37038, Part XIV (1995), p. 86.

Mostly hydrophobic color couplers, but also other hydrophobic components of the layers, are usually in high-boiling organic solvents dissolved or dispersed. These solutions or dispersions are then in one emulsified aqueous binder solution (usually gelatin solution) and lie after drying the layers as fine droplets (0.05 to 0.8 µm through knife) in the layers.

Suitable high-boiling organic solvents, methods for incorporation into the layers of a photographic material and other methods, chemical Introducing connections into photographic layers can be found in Research Disclosure 37254, Part 6 (1995), p. 292.

The usually between layers of different spectral sensitivity arranged non-light-sensitive intermediate layers can contain agents which an undesirable diffusion of developer oxidation products from a photosensitive to another photosensitive layer with different prevent spectral sensitization.

Suitable connections (white coupler, scavenger or EOP catcher) can be found in Research Disclosure 37254, Part 7 (1995), p. 292 and in Research Disclosure 37038, Part III (1995), p. 84.

The photographic material can also contain UV light-absorbing compounds, whiteners, spacers, filter dyes, formalin scavengers, light stabilizers, anti-oxidants, D _min dyes, additives to improve the stability of dyes, couplers and whites as well as to reduce the color fog, plasticizers (latices) , Biocide and others included.

Suitable compounds can be found in Research Disclosure 37254, Part 8 (1995), P. 292 and in Research Disclosure 37038, parts IV, V, VI, VII, X, XI and XIII (1995), p. 84 ff.

The layers of color photographic materials are typically hardened, i.e. H., the binder used, preferably gelatin, is by suitable cross-linked chemical processes.

Suitable hardener substances can be found in Research Disclosure 37254, Part 9 (1995), p. 294 and in Research Disclosure 37038, Part XII (1995), page 86.

After imagewise exposure, color photographic materials become their character ter processed according to different processes. Details of the Procedures and chemicals required for this are in Research Disclosure 37254, part 10 (1995), p. 294 and in Research Disclosure 37038, parts XVI to XXIII (1995), p. 95 ff. Published together with exemplary materials.

Examples

In all cases, the optimal gold / sulfur or Selenium amount used. The indicated sensitivities were after full sensitization determined.

• 1. An emulsion of 88 mol% AgBr and 12 mol% AgI with an average grain diameter of 1.2 µm was used, with 82% of the projected area being hexagonal tabular grains with an average aspect ratio of 6: 1 and an average neighboring edge ratio take from 1.1.
• 2. A core-shell emulsion (91 mol% AgBr, 9 mol% AgI) with an average grain size of 1.0 μm was used
• 3. A core-shell emulsion (91 mol% AgBr, 9 mol% AgI) with an average grain size of 1.0 µm was used
• 4. An emulsion of 90 mol% AgBr and 10 mol% AgI with an average grain diameter of 1.0 µm was used, with 86% of the projected area being hexagonal tabular grains with an average aspect ratio of 6: 1 and an average neighboring edge ratio take from 1.2.

Dyes in the examples:

Substances according to the invention in the examples:

Claims (10)

1. A process for the chemical ripening of silver halide emulsions with (a) gold and (b) sulfur or selenium compounds in the presence of spectral sensitizers, characterized in that before or during the addition of the ripening substances, but after the precipitation, at least 10% by weight. % of the optimum amount of dye for the sensitivity and between 10 ^-6 and 10 ^-3 mol of compounds of the formulas I to IV per mol of silver halide wherein
X 0 or S,
R₁ H, Cl or C₁-C₄ alkyl,
R₂ H, -CO-, -COOR₆ or -SO₂-R₆,
R₃, R₄, R₅ independently of one another unsubstituted or substituted alkyl,
R₆ C₁-C₄ alkyl or phenyl,
m 5 to 12,
n 1 to 4,
o 1 to 3,
mean. 2. The method according to claim 1, characterized in that the pro portion of the silver halide emulsions used of at least 50% consist of hexagonal tab grains. 3. The method according to claim 1, characterized in that the pro portion of the silver halide emulsions used of at least 70% consists of hexagonal tab-grains, their neighbor edge ratio is between 2: 1 and 1: 1 and the tab grains Have aspect ratio of 5: 1 to 20: 1. 4. The method according to claim 1, characterized in that before or 10 to 95% by weight of the sensitizer during chemical ripening amount to be added. 5. The method according to claim 1, characterized in that Sensibili sator dyes are used whose oxidation potential is between +1.8 and +0.5 V and their excitation energy are between 1.7 and 27 eV. 6. The method according to claim 1, characterized in that the silver halide emulsion before or during chemical ripening additional polyvalent metal ions from the series of the following metals are added:
Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cde, Sn, Ba, Ce, Eu, W, Re, Os, Ir, Pt, Hg, TI, Pb. 7. The method according to claim 6, characterized in that more than valuable metal ions ions of the metals Mg, Ca, Mg, Fe, Ni, Cu, Zn, Cd, Pb, Ir, Pd and Pt can be used. 8. The method according to claim 6, characterized in that 10 ^-8 to 10 ^-1 mol of metal compound per mol of silver halide are used. 9. The method according to claim 6, characterized in that 10 ^-6 to 10 ^-5 moles of metal compound per mole of silver halide are used. 10. The method according to claim 1, characterized in that the silver halide emulsion a silver bromide iodide emulsion with 5 to 15 mol% Is silver iodide.