Digitally imageable flexo-printing plate with integrated barrier layer
A digitally imageable, photopolymerizable flexographic printing element that includes, disposed one above another in order, at least a dimensionally stable support, at least one photopolymerizable, relief-forming layer having a layer thickness of 300-6000 μm, including at least one elastomeric binder, an ethylenically unsaturated monomer, and a photoinitiator or a photoinitiator system, an oxygen-blocking barrier layer which is transparent to UVA light and has a layer thickness of 0.3-5 μm, a laser-ablatable mask layer having a layer thickness of 0.3-5 μm, including at least one elastomeric binder and a material which absorbs UV/VIS light, and a removable outer film, wherein the at least one relief-forming layer, the barrier layer and the mask layer are soluble or dispersible in an organic solvent, and the barrier layer includes at least one oxygen-blocking binder and an oligomeric or polymeric basic adhesion component.
1. A digitally imageable, photopolymerizable flexographic printing element comprising, disposed one above another in order, at least
(A) a dimensionally stable support,
(B) at least one photopolymerizable, relief-forming layer having a layer thickness of 300 to 7000 μm, comprising at least one elastomeric binder, an ethylenically unsaturated monomer, and a photoinitiator or a photoinitiator system,
(C) an oxygen-blocking barrier layer which is transparent to UVA light and has a layer thickness of 0.3 to 5 μm,
(D) a laser-ablatable mask layer having a layer thickness of 0.3 to 5 μm, comprising at least one elastomeric binder and a material which absorbs UV/VIS light, and
(E) a removable outer film,
wherein:
the layers (B), (C) and (D) are soluble or dispersible in an organic solvent,
the barrier layer (C) comprises at least one oxygen-blocking binder and an oligomeric or polymeric basic adhesion component,
the elastomeric binder of the laser-ablatable mask layer (D) is at least one selected from the group consisting of a polyamide, a polyvinyl acetate, an ethylene-vinyl acetate copolymer, a partially hydrolyzed polyvinyl acetate, a polyurethane, a nitrocellulose, and a polyvinylacetal,
the basic adhesion component of the barrier layer (C) is an oligomeric or polymeric polyvinylamine or polyethylenimine.
2. The digitally imageable, photopolymerizable flexographic printing element of claim 1 , wherein the oxygen-blocking binder of the barrier layer (C) comprises a partially hydrolyzed polyvinyl acetate having a degree of hydrolysis of 10 to 75 mol %.
3. The digitally imageable, photopolymerizable flexographic printing element of claim 1 , wherein the oxygen-blocking binder of the barrier layer (C) comprises a polyvinylacetal.
4. The digitally imageable, photopolymerizable flexographic printing element of claim 3 , wherein the polyvinylacetal is at least one selected from the group consisting of polyvinylformal, polyvinylethyral, polyvinylpropyral, polyvinylbutyral, and poly(vinylethyral-vinylbutyral).
5. The digitally imageable, photopolymerizable flexographic printing element of claim 1 , wherein the barrier layer (C) further comprises a filler.
6. The digitally imageable, photopolymerizable flexographic printing element of claim 5 , wherein the filler is SiO 2 or a silicate.
7. The digitally imageable, photopolymerizable flexographic printing element of claim 5 , Wherein the filler has an average particle size of 1 to 10 μm.
8. The digitally imageable, photopolymerizable flexographic printing element of claim 1 , wherein the oxygen-blocking barrier layer (C) comprises
50 to 99 wt % of the oxygen-blocking binder,
1 to 30 wt % of the basic adhesion component, and
0 to 50 wt % of fillers.
9. The digitally imageable, photopolymerizable flexographic printing element of claim 1 , wherein the oxygen-blocking barrier layer comprises 1 to 30 wt % of fillers.
10. The digitally imageable photopolymerizable flexographic printing element of claim 1 , wherein the material which absorbs UV-VIS light in the mask layer (D) is at least one selected from the group consisting of carbon black, graphite, carbon nanoparticles, and carbon nanotubes.
11. A method for producing a flexographic printing plate from the digitally imageable, photopolymerizable flexographic printing element of claim 1 , comprising (i) to (vi):
(i) removing the outer film (E),
(ii) writing a mask into the laser-ablatable mask layer (D) with an IR laser,
(iii) exposing the imaged flexographic printing element to UVA light through the resultant mask,
(iv) removing the remnants of the laser-ablatable mask layer (D), the barrier layer (C), and the unpolymerized fractions of the relief-forming layer (B), using a washout medium,
(v) drying the resultant flexographic printing plate, and
(vi) optionally post-exposing the dried flexographic printing plate to UVA and/or UVC light.
12. The method of claim 11 , wherein the washout medium in (iv) comprises aliphatic, cycloaliphatic or aromatic hydrocarbons and one or more alcohols.
13. The digitally imageable, photopolymerizable flexographic printing element of claim 5 , wherein the filler has an average particle size of 2 to 6 μm.