An imageable material can be used to form a mask element that in turn is useful for providing relief images such as in flexographic printing plates. The imageable material has, in order: (a) a transparent polymeric carrier sheet; (b) a non-ablatable light-to-heat converting having an average dry thickness of 1-5 μm and comprising: (i) an infrared radiation absorbing material at 0.1-5 weight %; (ii) a thermally crosslinked organic polymeric binder material; and (iii) non-thermally ablatable particles having an average particle size of 0.1-20 μm in an amount of 0.2-10 weight %; and (c) a non-silver halide thermally-ablatable imaging layer (IL) disposed on the LTHC layer, the IL comprising a second infrared radiation absorbing material and a UV-light absorbing material dispersed within one or more thermally-ablatable polymeric binder materials.