Digitally exposable flexographic printing element and method for producing flexographic printing plates

A method for producing flexographic printing plates, by using as starting material a digitally imagable, photopolymerizable flexographic printing element, comprising at least—arranged one above another in the order stated—

• (A) a dimensionally stable support,
• (B) at least one photopolymerizable relief-forming layer which is dispersible or soluble in organic solvents and has a layer thickness of 300 μm to 6000 μm, comprising at least one elastomeric binder, an ethylenically unsaturated monomer, and a photoinitiator or photoinitiator system,
• (C) a barrier layer for oxygen, which is transparent for UVA light, and which has a layer thickness of 0.3 μm to 5 μm,
• (D) a laser-ablatable mask layer with a layer thickness of 0.3 μm to 5 μm comprising at least one elastomeric binder and materials that absorb UV/VIS light, the layer thickness and/or the amount of the light-absorbing materials being made such that the optical density of the layer for UVA radiation is 2 to 5, and
• (E) optionally a removable top film,
• where both the barrier layer (C) and the laser-ablatable mask layer (D) are water-soluble or water-dispersible, comprising the following method steps:
• (0) removing the top film (E) if present,
• (1) writing a mask into the laser-ablatable mask layer (D) by means of an IR laser,
• (2) exposing the imaged flexographic printing element with UVA radiation through the mask formed,
• (3) removing residues of the laser-ablatable mask layer (D) and the barrier layer (C) using an aqueous washout medium which comprises at least 90 wt % of water,
• (4) removing unpolymerized fractions of the relief-forming layer (B) using an organic washout medium to make a resulting flexographic printing plate,
• (5) drying the resulting flexographic printing plate, and
• carrying out aftertreatment with UVA and/or UVC light.