Printing form precursor, a process for making the precursor, and a method for preparing a printing form from the precursor
The invention pertains to a photosensitive element, particularly a photopolymerizable printing form precursor; a method of preparing the photosensitive element to form a printing form for use in relief printing; and, a process of making the photosensitive element. The printing form precursor includes a layer of a photosensitive composition, a digital layer that is adjacent to a side of the photosensitive layer, and a cell pattern layer that is disposed between the photosensitive layer and the digital layer. The cell pattern layer includes a plurality of features, and is composed of an ink that is opaque to actinic radiation and transparent to infrared radiation. Since the cell pattern layer is integral with the printing form precursor, digital imaging can occur rapidly with relatively low resolution optics to form a mask without needing to also form a microcell pattern of the digital layer.
1. A printing form precursor comprising:
a photopolymerizable layer comprising a first binder, a monomer, and a photoinitiator;
an infrared ablation layer that is ablatable by infrared radiation and opaque to non-infrared actinic radiation, the infrared ablation layer comprising:
(i) at least one infrared absorbing material;
(ii) a radiation opaque material, wherein (i) and (ii) can be the same or different; and
(iii) at least one second binder; and
a pattern layer that is disposed between the photopolymerizable layer and the infrared ablation layer, and comprises a plurality of features in which each feature has an area between 5 to 750 square microns and is composed of an ink that is opaque to actinic radiation and transparent to infrared radiation; wherein the infrared ablation layer is for forming an in-situ mask by infrared ablation during the conversion of the printing form precursor to a printing form.
2. The printing form precursor of claim 1 wherein the pattern layer is printed on a surface of the photopolymerizable layer opposite a support.
3. The printing form precursor of claim 1 wherein the pattern layer is printed onto a surface of the infrared ablation layer that will be adjacent to and contacting a surface of the photopolymerizable layer.
4. The printing form precursor of claim 1 wherein the ink is a cyan ink.
5. The printing form precursor of claim 1 wherein the ink contains a UV absorbing material.
6. The printing form precursor of claim 1 wherein the infrared ablation layer has a transmission optical density of greater than 2.0.