Patent ID: 8501388

Claim:
A method of preparing a laser-ablatable element comprising applying to a substrate, multiple formulations each comprising a coating solvent, a laser-ablatable polymeric binder, and an infrared radiation absorbing compound, to provide multiple sub-layers on the substrate, such that the infrared radiation absorbing compound concentration is different in each adjacent pair of sub-layers so that the concentration is always greater in each sub-layer that is closer to the substrate, and the concentration is progressively greater in the sub-layers as they are closer to the substrate after the coating solvent is removed, wherein the multiple sub-layers provide a relief-forming layer so that the sub-layer farthest from the substrate provides a relief-image forming surface, wherein the infrared radiation-absorbing compound is present in the relief-forming layer in a concentration profile throughout depth x from the relief-image forming surface so that the absorption coefficient profile α(x) is substantially in accordance with the following equation: α ⁡ ( x ) = 1 β - x ⁢ ⁢ wherein ⁢ ⁢ β ≤ F ρ ⁢ ⁢ C p ⁡ ( T c - T 0 ) wherein F is the fluence (energy per unit area) of an infrared radiation source when it is used to irradiate the relief-forming layer surface, ρ is the density of the relief-forming layer, C p is the heat capacity of the relief-forming layer, T O is the initial temperature of the relief-forming layer and T c is critical ablation temperature of the relief-forming layer.