The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 04, 1986
Filed:
Oct. 08, 1981
Derek H Barton, Gif-sur-Yvette, FR;
Irena Y Bronstein-Bonte, Newton, MA (US);
Lloyd D Taylor, Lexington, MA (US);
Polaroid Corporation, Cambridge, MA (US);
Abstract
Optical filter agents and photographic products and processes using same are disclosed. The optical filter agents are pH-sensitive hydrazone compounds conforming to the following structural formula: ##STR1## where R is any group which can provide a double bond for conjugation with the ##STR2## portion of the compound to provide light-absorbing capability or color for the agent at a pH above its pKa, X is a substituent of R providing at least one electron-withdrawing group and each R' can be defined as any substituent that does not impair the light-absorbing capacity of the compound at a pH above the pKa thereof. The pH-sensitive optical filter agents have a highly colored light-absorbing form at a pH above the pKa and are substantially non-absorbing at a pH below the pKa. The pH-sensitive optical filter agents are useful in photographic film units and processes for the protection of photoexposed photosensitive elements against the occurrence of fogging during in-light development.