A method of improving performance of a relief image printing plate on a printing cylinder which includes mounting a compressible cushion element on a surface of the printing cylinder. The surface of the cushion element that is contactable with the relief image printing plate is a low friction surface that allows a relief image printing plate to slide freely across its surface and settle into position on the printing cylinder. The use of a cushion element having a low friction surface reduces smut and improves registration of the printing plate on the printing cylinder.
1. A method of improving the performance of a relief image printing plate on a printing cylinder, the method comprising the steps of:
a) mounting a compressible cushion element on a surface of the printing cylinder, wherein the compressible cushion element comprises a compressible layer selected from the group consisting of an elastomer, rubber, foam and combinations of one or more of the foregoing, wherein the cushion element comprises a low friction surface that is contactable with the relief image printing plate, and wherein a coefficient of static friction between the cushion element and the relief image printing plate is less than 0.65; and
b) mounting the relief image printing plate on the low friction surface of the compressible cushion element,
whereby the low friction surface of the cushion element allows the relief image printing plate to slide across its surface and settle into position on the printing cylinder.
2. The method according to claim 1 wherein the compressible cushion element comprises
an adhesive layer that is capable of being affixed to the surface of the printing cylinder; and
(ii)
wherein the compressible layer comprises a low friction surface provided thereon by a method comprising one of:
(i) incorporating a low friction additive into the compressible layer; or
(ii) providing a top layer on the compressible layer, said top layer comprising a low friction additive.
3. The method according to claim 2 , wherein the compressible layer has the low friction additive dispersed therein to provide the low friction surface on the compressible layer.
4. The method according to claim 2 , wherein a top layer comprising a low friction additive is disposed on the compressible layer.
5. The method according to claim 4 , wherein the top layer is applied to the compressible layer of the cushion element by a method selected from the group consisting of spraying, roll coating, extrusion, curtain coating, and combinations of one or more of the foregoing.
6. The method according to claim 5 , wherein the top layer is dried-in-place or thermally or UV-cured, whereby the top layer is firmly attached to the compressible layer.
7. The method according to claim 2 , wherein the low friction additive is selected from the group consisting of organosilicones, silicone polymers, siliconized urethane acrylates, silicon surfactants, fluorocarbons, silicone acrylates, silicone methacrylates, fluorinated acrylates, fluorinated methacrylates, fluoropolymers, waxes, silicas, glass microspheres, ceramic microspheres, polymer microspheres and combinations of one or more of the foregoing.
8. The method according to claim 7 , wherein the low friction additive comprises at least one material selected from the group consisting of ceramic microspheres, silicone urethane acrylates and mixtures thereof.
9. The method according to claim 2 , wherein the slide angle between the low friction surface of the cushion element and the relief image printing plate is less than about 33°.
10. The method according to claim 9 , wherein the slide angle between the low friction surface of the cushion element and the relief image printing plate is less than about 30°.
11. The method according to claim 2 , wherein the resilience of the cushion element is between about 10 and 65%.
12. The method according to claim 1 , wherein the surface of the cushion element that is contactable with the relief image printing plate is continuous.
13. The method according to claim 1 , wherein the surface of the cushion element that is contactable with the flexographic printing plate comprises an open cell relief or longitudinal protrusions.
14. The method according to claim 1 , wherein the cushion element has a Shore A durometer of between about 40 and about 80.
15. The method according to claim 1 , wherein the relief image printing plate comprises a metallic substrate layer and a photopolymerizable layer.
16. The method according to claim 15 , wherein the relief image printing plate has a thickness between about 12 and 107 mils.
17. The method according to claim 16 , wherein the relief image printing plate has a total thickness of less than about 25 mils.
18. A low-friction compressible cushion element used for cushioning a relief image printing plate on a printing cylinder, the cushion element comprising:
a) an adhesive layer that is capable of being affixed to a surface of the printing cylinder; and
b) a compressible layer comprising a material selected from the group consisting of an elastomer, rubber, foam and combinations of one or more of the foregoing, and having a low friction surface provided thereon by a method comprising one of:
(i) incorporating a low friction additive into the compressible layer; or
(ii) providing a top layer on the compressible layer, said top layer comprising a low friction additive.
19. The low-friction compressible cushion element according to claim 18 , wherein the compressible layer has the low friction additive dispersed therein to provide the low friction surface on the compressible layer.
20. The low-friction compressible cushion element according to claim 18 , wherein a top layer comprising a low friction additive is disposed on the compressible layer.
21. The low-friction compressible cushion element according to claim 18 , wherein the low friction additive is selected from the group consisting or organosilicones, silicone polymers, siliconized urethane acrylates, silicon surfactants, fluorocarbons, silicone acrylates, silicone methacrylates, fluorinated acrylates, fluorinated methacrylates, fluoropolymers, waxes, silicas, glass microspheres, ceramic microspheres, polymer microspheres and combinations of one or more of the foregoing.
22. The low-friction compressible cushion element according to claim 21 , wherein the low friction additive comprises at least one material selected from the group consisting of ceramic microspheres, silicone urethane acrylates and mixtures thereof.