Photographic bleach compositions and methods of photographic processing
US5334491A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 22, 1993 |
| Grant date | Aug 2, 1994 |
| Priority date | — |
| Expiry date | Sep 22, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C7/42
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
Bleach compositions and methods that are improvements over those provided by Fyson, U.S. Pat. No. 4,294,914, are disclosed. A highly preferred bleach composition of this invention (a) has the ferric complex of methyliminodiacetic acid as a bleaching agent, and additionally comprises (b) at least 0.9 mole of acetic acid per liter, (c) from about 15 to about 35 grams per liter of potassium bromide; and (d) has a pH of from about 2.5 to about 4.0. This invention includes the discovery of a synergistic bleaching coaction of a bleach (i) comprising an alkyliminodiacetic acid such as methyliminodiacetic acid, and (ii) which has a pH of from about 3.5 to about 4.5 , and (iii) in which the amount of ferric iron is from about 2 to about 16 grams per liter. This coaction between iron levels and pH was previously unknown and was unexpected. Bleach formulations of this invention can be used in the processing of color photographic materials, such as film.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.