Photographic bleaching compositions and method of photographic processing using mixture of ferric complexes
US5693456A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 19, 1996 |
| Grant date | Dec 2, 1997 |
| Priority date | — |
| Expiry date | Jun 19, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C7/42
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A bleaching composition is a mixture of two ferric complexes with two different aminopolycarboxylic acid complexing ligands. The first complex is formed of a biodegradable aminopolycarboxylic acid, and acts as the primary bleaching agent. The second complex is formed of a less biodegradable aminopolycarboxylic acid, and acts to inhibit biological growth and rust formation. The molar ratio of the first complex to the second complex is at least 2:1. The first complexing ligand is iminodiacetic acid or an alkyliminodiacetic acid. The second complexing ligand is either ethylenediaminetetraacetic acid or propylenediaminetetraacetic acid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.