Method of controlling surface roughness of a flexographic printing plate

摘要

A method of controlling surface roughness of a flexographic printing element during thermal processing is provided. An imaged and exposed relief image printing element is thermally developed to remove the portions of at least one layer of photopolymer that are not crosslinked and cured by using a blotting material. The blotting material is separated from the at least one layer of photopolymer. Thereafter, a smooth material is inserted between the surface of the at least one layer of photopolymer and the blotting material, applying pressure and heat. In the alternative, after the relief image printing element is removed from the thermal processor, a polymeric film is laminated onto the relief image printing element using heat and pressure. The surface roughness of the relief image printing element is reduced, allowing for increased solid ink density on solid areas printed using the relief image printing element.

主权项

1. A method of making a relief image printing element with reduced surface roughness allowing for increased solid ink density when said relief image printing element is used for printing, wherein the relief image printing element comprises at least one layer of photopolymer that has been selectively imagewise exposed to actinic radiation to selectively crosslink and cure portions of the at least one layer of photopolymer, wherein the portions of the at least one layer of photopolymer that are crosslinked and cured form the relief image and the portions of the at least one layer of photopolymer that are not crosslinked and cured are removable in a subsequent development step, the method comprising in order the steps of:
a) thermally developing the relief image printing element to remove the portions of the at least one layer of photopolymer that are not cross-linked and cured by:
i) heating the at least one layer of photopolymer to a sufficient temperature to soften uncured portions of the at least one layer of photopolymer;ii) causing contact between the at least one layer of photopolymer and a blotting material, wherein when the blotting material contacts the at least one layer of photopolymer, the softened uncured photopolymer portions of the at least one layer of photopolymer are absorbed into the blotting material; andiii) separating the blotting material from the at least one layer of photopolymer; b) contacting the at least one layer of photopolymer with a smooth flexible sheet material while pressure and heat are applied to the smooth flexible sheet material in forcing it into contact with the at least one layer of photopolymer; and c) separating the smooth flexible sheet material from the at least one layer of photopolymer.