US3920667A
Expired / Lapsed
US
⏱️ 0.0 years remaining
3,3-DI-(Substituted azaphenanthen-8-yl)phthalides and naphthalides
Assignee: Polaroid Corp
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Filing: 1973-09-17
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Granted: 1975-11-18
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Expires: 1993-09-17
Abstract
Abstract This invention relates to a class of phthalein indicator dyes useful as optical filter agents in photographic processes to protect a selectively exposed photosensitive material from further exposure during processing in the presence of indicident light. Such dyes comprise 3,3-disubstituted phthalides and 3,3disubstituted naphthalides wherein the 3,3 substituents are parahydroxy polycyclic aryl radicals possessing a nitrogen atom included in the ring system adjacent to the para-hydroxy group.
Inventors
- 👤 Elbert M Idelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:48
CPC Classifications
G; G03; G03C; G03C8/00; G03C8/42; G03C8/44; G03C8/48
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
6 words
AN INDICATOR DYE HAVING THE FORMULA:
Claim 2
Dependent Claim
6 words
AN INDICATOR DYE HAVING THE FORMULA:
Claim 3
Dependent Claim
14 words
An indicator dye as defined in claim 1 wherein said dye is a phthalide.
Claim 4
Dependent Claim
1 words
Di-(5-hydroxy-4-azaphenanthren-8-yl)77carboxyphthalide
Claim 5
Dependent Claim
1 words
Di-(5-hydroxy-4-azaphenanthren-8-yl)77carboxyphthalide
Claim 6
Dependent Claim
1 words
Di-(6-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
Claim 7
Dependent Claim
1 words
Di-(6-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |