Patent ID: 8084182

Claim:
A negative-working, on-press developable imageable element comprising a substrate having thereon an imageable layer comprising: a radically polymerizable component, an initiator composition capable of generating free radicals sufficient to initiate polymerization of free radically polymerizable groups upon exposure to imaging infrared radiation, a primary polymeric binder that has a backbone to which are attached pendant poly(alkylene oxide) side chains, cyano groups, or both, and is optionally present in the form of discrete particles, and an infrared radiation absorbing dye that upon exposure to thermal irradiation, changes from colorless to a visible color or from one visible color to another visible color, providing a ΔE of at least 5 between the exposed and non-exposed regions of said imageable layer within 3 hours of its exposure to 300 ml/cm 2 at a laser power of 15 Watts, wherein ΔE=(ΔL* 2 +Δa* 2 +Δb* 2 ) 1/2 and is the measure of the difference in color expressed in terms of CIELAB 1976 coordinates L*, a*, and b*, between imaged or exposed regions and the non-imaged or non-exposed regions of the imageable layer, as determined before development, and wherein the infrared radiation absorbing dye comprises a cyanine dye chromophore that is represented by the following Structure (CHROMOPHORE): wherein Q 1 and Q 2 are the same or different substituted or unsubstituted alkoxycarbonyl groups, each alkoxy group having 1 to 5 carbon atoms, A and A′ are independently —S—, —O—, —NH—, —CH 2 —, or —CR′R″ groups wherein R′ and R″ are independently substituted or unsubstituted alkyl groups, or R′ and R″ together can form a substituted or unsubstituted cyclic group, Z represents the additional carbon atoms needed to provide a 5- to 7-membered carbocyclic ring, Z 1 and Z 2 are independently substituted or unsubstituted benzo or naphtho condensed rings, and R 1 ′ and R 2 ′ are independently substituted or unsubstituted cycloalkyl, or aryl groups.