US4184878A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the manufacture of photographic silver halide emulsions containing silver halide crystals of the twinned type
Assignee: Ilford Imaging UK Ltd
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Filing: 1978-11-30
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Granted: 1980-01-22
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Expires: 1998-11-30
Abstract
Abstract A method of preparing photograhic silver iodide, containing emulsions is provided. The silver halide crystals in said emulsions are of the twinned type and the method comprises the steps of (a) forming in a colloid dispersing medium silver halide crystals containing at least 90 mole % iodide, these said crystals being predominantly of the hexagonal lattice structure and then chemically sensitizing the said silver halide crystals which contain at least 90 mole % iodide, (b) mixing in the dispersing medium containing the said silver halide crystals an aqueous solution of a silver salt and an aqueous solution of an alkali metal or ammonium bromide or chloride or mixtures thereof so forming twinned silver halide crystals containing iodide and the halide or halides being added, (c) adding a silver halide solvent to the dispersing medium and so causing the growth of the twinned crystals by Ostwald ripening, optionally (d) causing the twinned crystals to increase in size by adding to the colloidal dispersion further aqueous silver salt solution and further alkali metal or ammonium halide and then finally optionally (e) removing the water-soluble salts formed and chemically sensitizing the surface of the silver halide crystals of the emulsion. The new photographic emulsions exhibit a high internal sensitivity and covering power and contrast on development.
Inventors
- 👤 Trevor J. Maternaghan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 11:19
CPC Classifications
G; G03; G03C; G03C1/00; G03C1/005; G03C1/0051; G03C1/06; G03C1/08; G03C1/09; G03C1/10; G03C2001/0058; G03C1/015; G03C2001/0156; G03C1/035; G03C2001/03535; G03C2001/03552; G03C2001/03558; G03C2001/03594; G03C2200/00; G03C2200/43; G03C2200/44
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
184 words
A method of preparing a silver halide emulsion of the twinned type which comprises the steps of (a) forming in a colloid dispersing medium silver halide crystals containing at least 90 mole % iodide, these said crystals being predominantly of the hexagonal lattice structure and then chemically sensitising the said silver halide crystals which contain at least 90 mole % iodide, (b) mixing in the dispersing medium containing the said silver halide crystals an aqueous solution of a silver salt and an aqueous solution of an alkali metal or ammonium bromide or chloride or mixtures thereof so forming twinned silver halide crystals containing iodide and the halide or halides being added, (c) adding a silver halide solvent to the dispersing medium and so causing the growth of the twinned crystals by Ostwald ripening, optionally (d) causing the twinned crystals to increase in size by adding to the colloidal dispersion further aqueous silver salt solution and further alkali metal or ammonium halide and then finally optionally (e) removing the water-soluble salts formed and chemically sensitising the surface of the silver halide crystals of the emulsion.
Claim 2
Independent Claim
184 words
A method of preparing a silver halide emulsion of the twinned type which comprises the steps of (a) forming in a colloid dispersing medium silver halide crystals containing at least 90 mole % iodide, these said crystals being predominantly of the hexagonal lattice structure and then chemically sensitising the said silver halide crystals which contain at least 90 mole % iodide, (b) mixing in the dispersing medium containing the said silver halide crystals an aqueous solution of a silver salt and an aqueous solution of an alkali metal or ammonium bromide or chloride or mixtures thereof so forming twinned silver halide crystals containing iodide and the halide or halides being added, (c) adding a silver halide solvent to the dispersing medium and so causing the growth of the twinned crystals by Ostwald ripening, optionally (d) causing the twinned crystals to increase in size by adding to the colloidal dispersion further aqueous silver salt solution and further alkali metal or ammonium halide and then finally optionally (e) removing the water-soluble salts formed and chemically sensitising the surface of the silver halide crystals of the emulsion.
Claim 3
Dependent Claim
20 words
A method according to claim 1 wherein the chemical sensitisation in step (a) is gold or another noble metal sensitisation.
Claim 4
Dependent Claim
16 words
A method according to claim 2 wherein the other noble metal is platinum, iridium or rhodium.
Claim 5
Dependent Claim
22 words
A method according to claim 1 wherein the chemical sensitisation in step (a) is effected by a compound of a heavy metal.
Claim 6
Dependent Claim
18 words
A method according to claim 4 wherein the heavy metal compound is a salt of lead or bismuth.
Claim 7
Dependent Claim
18 words
A method according to claim 1 wherein the chemical sensitisation in step (a) is sulphur or selenium sensitisation.
Claim 8
Dependent Claim
16 words
A method according to claim 1 wherein the chemical sensitisation in step (a) is reduction sensitisation.
Claim 9
Dependent Claim
20 words
A method according to claim 7 wherein the reducing agent used is a stannous salt, thiourea, a hydrazine or formaldehyde.
Claim 10
Dependent Claim
18 words
A method according to claim 1 wherein two types of chemical sensitisation are carried out in step (a).
Claim 11
Dependent Claim
18 words
A method according to claim 9 wherein the two types of chemical sensitisation are gold and sulphur sensitisation.
Claim 12
Dependent Claim
43 words
A method according to either claim 2 or claim 6 wherein the sensitisation is carried out at a fixed pAg between 8 and 9 and at a fixed pH between 5 and 7 at an elevated temperature between 50° C. and 60° C.
Claim 13
Dependent Claim
18 words
A method according to claim 5 wherein the sensitisation is carried out at a pH of approximately 3.
Claim 14
Dependent Claim
45 words
A method according to claim 1 wherein step (d) is carried out and the silver halide crystals formed in step (b) constitute the core of final silver halide crystals and the halide added in step (d) constitutes the shell of the final silver halide crystals.
Claim 15
Dependent Claim
44 words
A method according to claim 1 where in step (b) the halide precipitated during at least the first part of the step is predominantly chloride and in step (d) the halide precipitated at least during the final part of the step is predominantly bromide.
Claim 16
Dependent Claim
20 words
A method according to claim 1 wherein the surface of the silver halide crystals are chemically sensitised in step (e).
Claim 17
Dependent Claim
15 words
A method according to claim 15 wherein the chemical sensitisation is sulphur and gold sensitisation.
Claim 18
Dependent Claim
19 words
A method according to claim 1 wherein the surface of the silver halide crystals is fogged in step (e).
Claim 19
Dependent Claim
29 words
A method according to claim 17 wherein the fogging is carried out by use of a reducing agent together with a compound of a metal more electro-positive than silver.
Claim 20
Dependent Claim
20 words
A method according to claim 18 wherein an electron-trapping compound is adsorbed on the surface of the silver halide crystals.
Claim 21
Dependent Claim
10 words
A silver halide emulsion when prepared according to claim 1.
Claim 22
Dependent Claim
18 words
Photographic material which contains at least one layer which contains a silver halide emulsion according to claim 20.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-01-21 | 1983-07-23 | 1984-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-01-21 | 1987-07-23 | 1988-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-01-21 | 1991-07-23 | 1992-01-22 | $7700.00 | Window Closed / Lapsed |