Green sensitizing dyes for variable contrast photographic elemen

Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing

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430576, G03C 1005

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active

052197239

ABSTRACT:
A variable contrast photographic element containing a light sensitive silver halide emulsion layer is disclosed wherein the silver halide is sensitized with a benzimidazolooxacarbocyanine dye of the following formula (I) in an amount less than that required to impart maximum sensitivity to all of the silver halide in the emulsion. ##STR1## In formula (I), R.sup.1, R.sup.2, R.sup.6 and R.sup.7 each independently represent hydrogen, halogen, hydroxy, or substituted or unsubstituted alkyl, alkenyl, alkoxy, alkylamino, alkylthio, aryl, aryloxy, arylamino, or arylthio. R.sup.3 and R.sup.4 each independently represent substituted or unsubstituted alkyl. R.sup.5 represents a substituent containing an electron withdrawing group. X represents a counterion as needed to balance the charge of the molecule. Use of dyes of formula (I) having an R.sup.5 substituent which contains an electron withdrawing group has been found to beneficially reduce the sensitivity of variable contrast photographic elements at wavelengths longer than 570 nm, thereby enhancing safelight tolerance, while still maintaining good spectral sensitivity at wavelengths in the green region less than 560 nm.

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