Abstract: A photographic imaging system is disclosed comprised of a hardenable organic component containing ethylenic unsaturation sites and an initiator system for ethylenic addition. The initiator system is comprised of an electron acceptor activator, an electron donor activator, and, acting as a photosensitizer, a dye capable of absorbing imaging radiation. The dye has a reduction potential related to that of the electron acceptor activator and an oxidation potential related to that of the electron donor activator to permit each to release a free radical upon excitation of the photosensitizer by exposure to actinic radiation.

Abstract: A negative working photoresist is disclosed responsive to imaging radiation of a wavelength longer than 550 nm comprised of an organic film forming component containing ethylenic unsaturation and capable of selective immobilization by addition at the site of ethylenic unsaturation and activator and photosensitizer coinitiators for ethylenic addition. The activator is an azinium salt activator, and the photosensitizer is a dye having its principal absorption peak at a wavelength longer than 550 nm and having a reduction potential which in relation to that of said azinium salt activator is at most 0.1 volt more positive.

Abstract: An imaging composition is disclosed comprised of an organic component containing ethylenic unsaturation sites and capable of selective hardening by addition at the sites of ethylenic unsaturation, an azinium salt activator, a photosensitizer having a reduction potential which in relation to the reduction potential of the azinium salt activator is at most 0.1 volt more positive, and an image enhancing amount of benzene substituted with an electron donating amino group and one or more groups capable of imparting a net Hammett sigma value electron withdrawing characteristic of at least +0.20 volt to said benzene ring.

Abstract: A negative working photoresist is disclosed responsive to imaging radiation of a visible wavelength shorter longer than 550 nm comprised of an organic film forming component containing ethylenic unsaturation and capable of selective immobilization by addition at the site of ethylenic unsaturation and activator and photosensitizer coinitiators for ethylenic addition. The activator is an azinium salt activator, and the photosensitizer is a dye having its principal absorption peak at a wavelength shorter than 550 nm and having a reduction potential which in relation to that of said azinium salt activator is at most 0.1 volt more positive. When the dye is a keto dye, it exhibits when excited by imaging radiation an intersystem crossing efficiency to a triplet state of less than 10 percent.

Abstract: A photographic imaging system is disclosed comprised of an imaging dye or a precursor thereof, a hardenable organic component containing ethylenic unsaturation sites and capable of imagewise modulating mobility of the dye or dye precursor as a function of addition at the sites of ethylenic unsaturation, and coinitiators for ethylenic addition. The coinitiators include an azinium salt activator and a photosensitizer which is a dye exhibiting a reduction potential which in relation to that of said ionized azinium salt activator is at most 0.1 volt more positive, with the further proviso that, when the photosensitizer is a keto dye having its principal absorption peak at a wavelength shorter than 550 nm, it exhibits when excited by imaging radiation an intersystem crossing efficiency to a triplet state of less than 10 percent.