Photographic processing composition and method using organic catalyst for peroxide bleaching agent
AssigneeEastman Kodak Company
InventorTerrence Robert O'Toole
Life of this patent
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Abstract
Certain organic carbocyclic and heterocyclic compounds are useful catalysts for hydrogen peroxide bleaching agents in photographic processing methods. These compounds are oxidizable by hydrogen peroxide and reducible by silver metal at a pH of from 1 to 7, and have a chemically reversible redox couple of from about -0.20 to about +1.0 volts at the same pH. The hydrogen peroxide bleaching ability is enhanced by the presence of these compounds which can be used in the bleaching solution itself, or in a prebath solution. The combination of the organic compound with a transition metal ion co-catalyst provides a synergistic effect in bleaching acceleration.
Claims14
A method for processing a photographic element comprising:
- treating an imagewise exposed and developed photographic element with a solution that has a pH of from about 3 to about 5, is substantially free of ferric ions, and consists essentially of from about 0.1 to about 2 mol/l of a peroxide or a perborate or percarbonate peroxide precursor bleaching agent and from about 0.0005 to about 0.1 mol/l of an organic carbocyclic or heterocyclic compound which has the following properties:
- a) a reduced form which is oxidizable by peroxide or a peroxide precursor at a pH of from about 1 to about 7,
- b) an oxidized form which is reducible by silver metal in the presence of bromide or chloride at a pH of from about 1 to about 7, and
- c) a chemically reversible redox couple, versus a saturated calomel electrode, of from about -0.20 to about +1.5 volts at a pH of from about 1 to about 7,
- said organic carbocyclic or heterocyclic compound having a neutral or net positive charge, and being represented by any of the structures:
- ##STR3## wherein A1 and A2 are independently hydroxy or primary, secondary or tertiary amino,
- R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently hydrogen, halo, cyano, nitro, amide, sulfonamide, hydroxy, an ester, an ether, a primary, secondary or tertiary amino, an alkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbon atoms in the ring structure, a cycloalkyl group of 5 to 12 carbon atoms in the ring structure or a quaternized aliphatic or aromatic amine or imine, or
- any two adjacent groups chosen from R1, R2, R3, R4, R5, R6, R7, R8 and R9, can represent the carbon, nitrogen, oxygen and sulfur atoms necessary to complete a 5- to 12-membered fused carbocyclic or heterocyclic ring structure connected to the primary nucleus of structures (I)-(IV),
- Y is a sulfur, oxygen or nitrogen atom,
- X is an anion with a charge y of -1 to -3,
- m is the absolute value of the ratio of n to y, and
- n is 0 or a positive integer up to 3.
Dependencies are inferred from the claim text.