US3716362A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the removal of metallic silver from photographic material
Assignee: Novartis AG
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Filing: 1970-07-21
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Granted: 1973-02-13
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Expires: 1990-07-21
Abstract
Abstract A process for removing metallic silver from photographic materials is provided, wherein any sparingly soluble silver salts present are not attacked. This process comprises treating the photographic material with an acid bath free from anions that form sparingly soluble silver salts and which bath contains an oxidant and a complexing agent. The oxidant has a standard redox potential of at most +0.8 Volts and the complexing agent has a silver complex stability constant of at most 109 (liter/mole)2. This process is of special importance in carrying out the silver dye bleach negative-positive process. The main advantage of the process is the fact that it uses only a small number of bathes and no strong oxidants.
Inventors
- 👤 M Meier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:21
CPC Classifications
G; G03; G03C; G03C5/00; G03C5/26; G03C5/40; G03C5/44; G03C7/00; G03C7/28; G03C7/30; G03C7/42; G03C7/421
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
111 words
In a process for removing metallic silver without attacking any dyestuffs or sparingly soluble silver halides present from a photographic material comprising sparingly soluble silver halides and metallic silver distributed in at least one emulsion layer on a support by the steps of exposing, developing, reversal developing, dye bleaching, silver bleaching and fixing, the improvement which comprises treating said material after the first silver image developing bath with an acid bath free from anions that form sparingly soluble silver halides, said bath containing an oxidant selected from a copper (II) salt, a quinone or an iron (III) salt, and a complexing agent selected from allyl alcohol, a nitrile and a thio-ether.
Claim 2
Dependent Claim
111 words
In a process for removing metallic silver without attacking any dyestuffs or sparingly soluble silver halides present from a photographic material comprising sparingly soluble silver halides and metallic silver distributed in at least one emulsion layer on a support by the steps of exposing, developing, reversal developing, dye bleaching, silver bleaching and fixing, the improvement which comprises treating said material after the first silver image developing bath with an acid bath free from anions that form sparingly soluble silver halides, said bath containing an oxidant selected from a copper (II) salt, a quinone or an iron (III) salt, and a complexing agent selected from allyl alcohol, a nitrile and a thio-ether.
Claim 3
Dependent Claim
17 words
A process as claimed in claim 1, wherein a water-soluble aliphatic monothioether is used as complexing agent.
Claim 4
Dependent Claim
56 words
A process as claimed in claim 1, wherein the complexing agent is a monothioether of the formulaX1-R1-S-R2-X2 in which R1 and R2 which may be the same or different, each represents alkyl having at most three carbon atoms, and X1 and X2 which may be the same or different, each represents hydrogen or hydroxyl or carboxyl.
Claim 5
Dependent Claim
35 words
A process as claimed in claim 1, wherein the complexing agent is a monothioether of the formula in which X1 and X2 which may be the same or different, each represents hydrogen, hydroxyl or carboxyl.
Claim 6
Dependent Claim
14 words
A process as claimed in claim 1, wherein the silver halide is silver bromide.
Claim 7
Dependent Claim
17 words
A process as claimed in claim 1, wherein the pH value of the bath is below 6.
Claim 8
Dependent Claim
22 words
A process as claimed in claim 1, wherein the metallic silver and the silver halide are present in the same emulsion layer.
Claim 9
Dependent Claim
14 words
A process as claimed in claim 1, carried out in a reversal development process.
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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) | 1976-02-13 | 1976-08-14 | 1977-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-13 | 1980-08-14 | 1981-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-13 | 1984-08-14 | 1985-02-13 | $7700.00 | Window Closed / Lapsed |