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US4477565A
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Method for preparing photosensitive silver halide emulsion
Assignee: Polaroid Corp
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Filing: 1983-02-02
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Granted: 1984-10-16
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Expires: 2003-02-02
Abstract
Abstract Silver halide emulsions having tabular grains with a mean aspect ratio of at least 10 are prepared by inducing twinning on the (111) crystal plane in silver bromide grains and then growing the grains in a silver halide solvent solution for a time sufficient to provide said tabular grains.
Inventors
- 👤 Richard S. Himmelwright
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 18:39
CPC Classifications
G; G03; G03C; G03C1/00; G03C1/005; G03C1/0051; G03C1/06; G03C1/07; G03C2001/0055; G03C2001/0058; G03C1/015; G03C2001/0156; G03C2200/00; G03C2200/43
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
72 words
A method for forming a photosensitive silver halide emulsion wherein the grains are predominantly tabular grains which are multiply twinned on the (111) plane and possess a mean aspect ratio of at least 10 which comprises inducing twinning in feedstock silver bromide grains and then growing said grains in a silver halide solvent solution for a time sufficient to provide said tabular grains and substantially all of said feedstock grains have disappeared.
Claim 2
Independent Claim
72 words
A method for forming a photosensitive silver halide emulsion wherein the grains are predominantly tabular grains which are multiply twinned on the (111) plane and possess a mean aspect ratio of at least 10 which comprises inducing twinning in feedstock silver bromide grains and then growing said grains in a silver halide solvent solution for a time sufficient to provide said tabular grains and substantially all of said feedstock grains have disappeared.
Claim 3
Dependent Claim
23 words
The method of claim 1 wherein said silver bromide grains are about 0.1 to 0.2 micrometers in mean volume diameter prior to twinning.
Claim 4
Dependent Claim
28 words
The method of claim 1 wherein said twinning is induced by adjusting the pAg from the pAg at which the grains are formed to about 9.8 to 11.8.
Claim 5
Dependent Claim
13 words
The method of claim 1 wherein said silver halide solvent is ammonium hydroxide.
Claim 6
Dependent Claim
12 words
The method of claim 1 wherein said silver halide solvent is 1,8-dihydroxy-3,6-dithia-octane.
Claim 7
Dependent Claim
15 words
The method of claim 1 wherein the mean aspect ratio is about 20 to 40.
Claim 8
Dependent Claim
19 words
The method of claim 4 wherein said pAg is adjusted by adding alkali bromide to said silver bromide grains.
Claim 9
Dependent Claim
20 words
The method of claim 1 which comprises adding alkali or ammonium iodide and/or chloride during said growing of said grain.
Claim 10
Dependent Claim
15 words
The method of claim 1 wherein said emulsion is about 80% by number tabular grains.
Claim 11
Independent Claim
108 words
A method for forming a photosensitive silver halide emulsion wherein the grains are predominantly tabular grains which are multiply twinned on the (111) plane and possess a mean aspect ratio of at least 10 which comprises the following steps, in sequence, (a) precipitating feedstock silver bromide grains at a pAg of not greater than about 9.7; (b) adjusting the pAg to between about 9.8 and 11.8 to induce twinning on the (111) crystal plane in said grains; and (c) growing said grains in a solution of a silver halide solvent for a time sufficient to provide said tabular grains and substantially all of said feedstock grains have dissappeared.
Claim 12
Independent Claim
108 words
A method for forming a photosensitive silver halide emulsion wherein the grains are predominantly tabular grains which are multiply twinned on the (111) plane and possess a mean aspect ratio of at least 10 which comprises the following steps, in sequence, (a) precipitating feedstock silver bromide grains at a pAg of not greater than about 9.7; (b) adjusting the pAg to between about 9.8 and 11.8 to induce twinning on the (111) crystal plane in said grains; and (c) growing said grains in a solution of a silver halide solvent for a time sufficient to provide said tabular grains and substantially all of said feedstock grains have dissappeared.
Claim 13
Dependent Claim
23 words
The method of claim 10 wherein said silver bromide grains formed in step (a) are about 0.1 to 0.2 micrometers mean volume diameter.
Claim 14
Dependent Claim
19 words
The method of claim 10 wherein said pAg is adjusted by adding alkali bromide to said silver bromide grains.
Claim 15
Dependent Claim
13 words
The method of claim 10 wherein said silver halide solvent is ammonium hydroxide.
Claim 16
Dependent Claim
12 words
The method of claim 10 wherein said silver halide solvent is 1,8-dihydroxy-3,6-dithia-octane.
Claim 17
Dependent Claim
20 words
The method of claim 10 which comprises adding alkali or ammonium iodide and/or chloride during said growing of said grains.
Claim 18
Dependent Claim
14 words
The method of claim 10 wherein said mean aspect ratio is 20 to 40.
Claim 19
Dependent Claim
13 words
The method of claim 10 wherein said emulsion is about 80% tabular grains.
References Cited (Backward Citations)
US4067739A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-16 | 1988-04-16 | 1988-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-16 | 1992-04-16 | 1992-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-16 | 1996-04-16 | 1996-10-16 | $7700.00 | Window Closed / Lapsed |