Direct positive silver halide emulsions containing quaternated merocyanine dyes

摘要

Quaternated merocyanine dyes for spectrally sensitizing direct positive silver halide emulsions having a first heterocyclic nucleus selected from the group consisting of a 2-isoxazolin-3-furyl-5-one, a 2- isoxazolin-3-thienyl-5-one, a 2-isoxazolin-3-pyrryl-5-one, a 2-pyrazolin- 3-furyl-5-one, a 2-pyrazolin-3-thienyl-5-one and a 2-pyrazolin-3-pyrryl-5- one nucleus, linked at the 4-carbon atom thereof through a methine chain to a second heterocyclic nucleus for completing the said quaternated merocyanine dye.