Thermally sensitive, multilayer imageable element
View Patent ↗Multi-layer, positive working, thermally sensitive imageable elements, useful as lithographic printing plate precursors, are disclosed. The elements comprises a substrate, an underlayer over the substrate, and a top layer over the underlayer. The top layer comprises polymeric material, which is a solvent soluble novolac resin or a derivative thereof. The polymeric material is a (a) novolac that has a weight average molecular weight of at least 10,000, a derivative thereof functionalized with polar groups, or a derivative thereof functionalized with quadruple hydrogen bonding entities; (b) a solvent soluble m-cresol/p-cresol novolac resins that comprises at least 10 mol % p-cresol and has a weight average molecular weight of at least 8,000, a derivative thereof functionalized with polar groups, or a derivative thereof functionalized with quadruple hydrogen bonding entities; or (c) a mixture thereof. The imageable elements have increased scuff resistance and are thus less susceptible to damage during handling.
1. An imageable element comprising, in order:
a substrate having a hydrophilic surface,
an underlayer comprising a first polymeric material over the hydrophilic surface of the substrate, and
a top layer comprising a second polymeric material over the underlayer,
in which:
the top layer is ink receptive and insoluble in an alkaline developer; and
the top layer and the underlayer are each removable by the alkaline developer following thermal imaging of the element; and
the second polymeric material is selected from the group consisting of:
solvent soluble novolac resins that have a weight average molecular weight of at least 18,000, derivatives thereof in which the novolac resin is functionalized with polar groups, derivatives thereof in which the novolac resin is functionalized with quadruple hydrogen bonding entities, and
mixtures thereof.
2. The element of claim 1 in which the alkaline developer is a solvent based developer.
3. The element of claim 1 in which the second polymeric material is either a solvent soluble m-cresol only novolac resin or a solvent soluble m-cresol/p-cresol novolac resin that has up to 10 mol % of p-cresol in which the novolac resin has a weight average molecular weight of at least 25,000.
4. The element of claim 1 in which the second polymeric material is either a solvent soluble m-cresol only novolac resin or a solvent soluble m-cresol/p-cresol novolac resin that has up to 10 mol % of p-cresol and in which the novolac resin is functionalized with QHB entities.
5. The element of claim 4 in which the weight average molecular weight of the novolac resin is at least 25,000.
6. The element of claim 1 in which the second polymeric material is a solvent soluble m-cresol/p-cresol novolac resin that comprises at least 10 mol % p-cresol and in which the novolac resin is functionalized with QHB entities.
7. The element of claim 6 in which the weight average molecular weight of the novolac resin is at least 25,000.
8. The element of claim 1 in which the novolac resin is prepared by solvent condensation.
9. The element of claim 8 in which the weight average molecular weight of the novolac resin is at least 25,000.
10. The element of claim 1 in which the second polymeric material is a solvent soluble m-cresol/p-cresol novolac resin that comprises at least 10 mol % p-cresol.
11. The element of claim 10 in which the weight average molecular weight of the novolac resin is at least 25,000.
12. The element of claim 10 in which the m-cresol/p-cresol novolac resin comprises 30 mol % to 60 mol % p-cresol.
13. The element of claim 10 in which the m-cresol/p-cresol novolac resin comprises 30 mol % to 40 mol % p-cresol.
14. The element of claim 13 in which the weight average molecular weight of the novolac resin is at least 25,000.
15. The element of claim 1 in which the second polymeric material is either a solvent soluble m-cresol only novolac resin or a solvent soluble m-cresol/p-cresol novolac resin that has up to 10 mol % of p-cresol and in which the novolac resin is functionalized with polar groups.
16. The element of claim 15 in which the weight average molecular weight of the novolac resin is at least 25,000.
17. The element of claim 1 in which the novolac resin comprises from 10% to 50% p-cresol and in which the weight average molecular weight of the novolac resin is at least 20,000.
18. The element of claim 1 in which the second polymeric material is a solvent soluble m-cresol/p-cresol novolac resin that comprises at least 10 mol % p-cresol in which the novolac resin and in which the novolac resin is functionalized with polar groups.
19. The element of claim 18 in which the m-cresol/p-cresol novolac resin comprises 30 mol % to 60 mol % p-cresol.
20. The element of claim 18 in which the m-cresol/p-cresol novolac resin comprises 30 mol % to 40 mol % p-cresol.
21. The element of claim 20 in which the m-cresol/p-cresol novolac resin has a weight average molecular weight of at least 25,000.
22. The element of claim 1 in which the imageable element additionally comprises a photothermal conversion material.
23. The element of claim 22 in which the photothermal conversion material is in the underlayer or in an absorber layer between the underlayer and the top layer.
24. The element of claim 23 in which the weight average molecular weight of the novolac resin is at least 25,000.
25. The element of claim 25 in which the second polymeric material is either a solvent soluble m-cresol only novolac resin or a solvent soluble m-cresol/p-cresol novolac resin that has up to 10 mol % of p-cresol.
26. A method for forming an image, the method comprising the steps of:
(A) thermally imaging an imageable element and forming an imaged element comprising imaged and unimaged regions;
in which the imageable element comprises:
a substrate having a hydrophilic surface,
an underlayer comprising a first polymeric material over the hydrophilic surface of the substrate, and
a top layer comprising a second polymeric material over the underlayer,
in which:
the top layer is ink receptive and insoluble in an alkaline developer; and
the top layer and the underlayer are each removable by the alkaline developer following thermal imaging of the element; and
the second polymeric material is selected from the group consisting of:
solvent soluble novolac resins that have a weight average molecular weight of at least 18,000, derivatives thereof in which the novolac resin is functionalized with polar groups, and derivatives thereof in which the novolac resin is functionalized with quadruple hydrogen bonding entities, and
mixtures thereof; and
(B) developing the imaged element in an alkaline developer and removing the imaged regions.
27. The method of claim 26 in which the developer is a solvent based developer.
28. The method of claim 26 in which imaging is carried out with a heated body.
29. The method of claim 26 in which the element additionally comprises a photothermal conversion material and imaging is carried out with an infrared laser.
30. The method of claim 29 in which the novolac resin has a weight average molecular weight of at least 25,000.
31. The method of claim 26 in which the second polymeric material is a novolac resin that has a weight average molecular weight of at least 25,000.
32. The method of claim 31 in which the developer is a solvent based developer.
33. The method of claim 32 in which the second polymeric material is a m-cresol/p-cresol novolac resin that comprises 30 mol % to 40 mol % p-cresol.
34. An image, formed by the steps of
(A) thermally imaging an imageable element and forming an imaged element comprising imaged and unimaged regions;
in which the imageable element comprises:
a substrate having a hydrophilic surface,
an underlayer comprising a first polymeric material over the hydrophilic surface of the substrate, and
a top layer comprising a second polymeric material over the underlayer,
in which:
the top layer is ink receptive and insoluble in an alkaline developer; and
the top layer and the underlayer are each removable by the alkaline developer following thermal imaging of the element; and
the second polymeric material is selected from the group consisting of:
solvent soluble novolac resins that have a weight average molecular weight of at least 18,000, derivatives thereof functionalized in which the novolac resin is with polar groups, and derivatives thereof in which the novolac resin is functionalized with quadruple hydrogen bonding entities, and
mixtures thereof; and
(B) forming the image by developing the imaged element in an alkaline developer and removing the imaged regions.
35. The image of claim 34 in which the second polymeric material is, novolac resin that has a weight average molecular weight of at least 25,000.
36. The image of claim 35 in which the developer is a solvent based developer.
37. The image of claim 36 in which the second polymeric material is a m-cresol/p-cresol novolac resin that comprises 30 mol % to 40 mol % p-cresol.