Method for generative production of relief printing plates by monomer diffusion through an integral mask layer
The invention relates to a method for generative production of relief printing plates, wherein a support with a polymeric substrate layer and a laser-ablatable mask layer is provided, the polymeric substrate layer containing a first binder. A mask with openings corresponding to pixels is produced by imagewise laser ablation of the mask layer. A liquid containing a reactive monomer is then applied over the surface of the mask-covered polymeric substrate layer, and the liquid or the reactive monomer diffuses through the openings of the mask into the polymeric substrate layer for a defined exposure time so as to form a relief. The excess liquid or the excess monomer and optionally the mask are removed from the surface, and the resulting relief is fixed by crosslinking.
1. A method for the production of relief printing plates comprising the following steps:
a) providing a support with a polymeric substrate layer and a laser-ablatable mask layer, wherein the polymeric substrate layer contains a first polymeric binder,
b) producing a mask with openings corresponding to pixels by imagewise laser ablation of the mask layer,
c) applying a liquid containing a reactive monomer over the surface of the mask,
d) diffusion of the reactive monomer through the openings of the mask into the polymeric substrate layer for a predetermined exposure time, wherein a relief is formed,
e) removing non-diffused monomer from the surface, and
f) fixing of the resulting relief by cross-linking.
2. The method according to claim 1 , wherein the polymeric substrate layer contains a photoinitiator.
3. The method according to claim 1 , wherein the substrate layer is free of reactive monomer or contains less than 10 wt. % of reactive monomer.
4. The method according to claim 1 , wherein the laser-ablatable mask layer contains a second polymeric binder and a light-absorbing component, wherein the diffusion rate of the reactive monomer in the second polymeric binder at room temperature is less than in the first polymeric binder.
5. The method according to claim 4 , wherein the second binder is polyvinyl alcohol, partially or highly saponified polyvinyl acetate, polyvinyl butyral, cellulose, nitrocellulose, polyethylene oxide-polyvinyl alcohol copolymers, polycyanoacrylate or polyamide.
6. The method according to claim 1 , wherein the application of the liquid to the mask in step c) takes place by immersion, roller application, spraying or doctoring.
7. The method according to claim 4 , wherein the light-absorbing component is carbon black, graphite, nanosized carbon black particles or carbon nanotubes.
8. The method according to claim 1 , wherein the first binder is styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-butadiene/styrene-styrene, styrene-isoprene-butadiene-styrene (SIBS), styrene-butadiene (SB) block copolymers, or ethylene propylene diene monomer (EPDM) rubber.
9. The method according to claim 1 , wherein the reactive monomer is ethylhexyl acrylate, hexanediol diacrylate, dodecanediol diacrylate, cyclohexyl acrylate, isobornyl acrylate, or the corresponding methacrylates.
10. The method according to claim 1 , wherein the liquid is free of photoinitiators.
11. The method according to claim 1 , wherein crosslinking of the relief according to step f) takes place by exposure to UV light.
12. The method according to claim 1 , wherein the diffusion rate of the reactive monomer in the first polymeric binder at room temperature is at least 0.5 μm/minute and at most 10 μm/minute.
13. The method according to claim 1 , wherein the exposure time in step c) is 1 minute to 60 minutes.
14. The method according to claim 1 , wherein the relief formed has a height of 5 μm to 500 μm.
15. The method according to claim 1 , wherein in producing the mask according to step b), the dimensions of the openings are greater than the relief elements to be produced.
16. The method according to claim 1 , wherein in producing the mask according to step b), in an area around the openings, the permeability of the mask for the liquid is increased by writing in of a dot matrix, wherein further openings are produced at the dots of the dot matrix.
17. The method according to claim 16 , wherein the dot matrix has a resolution of at least 5,000 dpi.
18. The method according to claim 5 , wherein the non-diffused monomer and the mask layer are rinsed off with a mixture of an alcohol and water in step e).