Method of manufacturing imaging compositions
View Patent ↗The present invention provides methods of forming and using thermally imageable composite elements which may be developed into lithographic printing plates. More specifically, the present invention provides a method of forming thermally imageable composite elements which provide substantial developer resistance in desired regions, while maintaining white light desensitivity and durability.
1. A method of forming a printing plate precursor comprising:
(a) exposing a printing plate precursor to ultraviolet light to form a white light-desensitized printing plate precursor, the printing plate precursor comprising:
(1) a substrate having a hydrophilic surface,
(2) a first layer applied to the substrate which is soluble in an aqueous alkaline solution, and
(3) a second layer applied to the first layer including a polymeric material, a base, and an effective amount of a quinonediazide to provide the second layer with substantial insolubility in an aqueous alkaline solution; and
(b) heating the ultraviolet light exposed precursor to form a positive-working imageable printing plate precursor.
2. The method of claim 1 wherein the quinonediazide consists of naphthoquinonediazide.
3. The method of claim 1 wherein the effective amount of quinonediazide is between 15 and 45 parts by weight of the second layer.
4. The method of claim 1 wherein the quinonediazide consists of a naphthoquinonediazide sulfonate ester of a cresol Novolac.
5. The method of claim 1 wherein the polymeric material includes a Novolac resin.
6. The method of claim 1 wherein the polymeric material includes an alkylated Novolac resin.
7. The method of claim 1 wherein the base includes sodium citrate, triethylamine, triethanolamine, aminomethylpropanol or 1-hyoxyethyl-2-alkylimideazoline.
8. The method of claim 1 wherein exposing the prescursor to ultraviolet light comprises exposing the prescursor to ultraviolet light for at least 10 seconds.
9. The method of claim 1 wherein exposing the prescursor to ultraviolet light comprises exposing the prescursor to ultraviolet light for at least 15 seconds.
10. The method of claim 1 wherein exposing the prescursor to ultraviolet light comprises exposing the prescursor to ultraviolet light for at least 30 seconds.
11. The method of claim 1 wherein exposing the prescursor to ultraviolet light comprises exposing the prescursor to ultraviolet light for at least 60 seconds.
12. The method of claim 1 wherein the hydrophilic substrate is an aluminum sheet.
13. The method of claim 1 wherein the first layer includes a binder soluble in an aqueous alkaline developer.
14. The method of claim 13 wherein the binder includes a polymeric material.
15. The method of claim 13 wherein the binder is a copolymer of N-phenylmaleimide, methacrylamide, and methacrylic acid.
16. The method of claim 1 wherein the first layer includes an infrared absorber.
17. The method of claim 1 wherein the first layer includes an infrared dye.
18. The method of claim 17 wherein the dye is represented by the structure:
19. The method of claim 1 wherein heating the precursor consists of heating the precursor in an oven at between about 100° C. and 200° C. for between about 100 seconds and 1000 seconds.
20. The method of claim 1 further comprising thermally imagewise exposing the heated precursor.
21. A method of forming a image on a printing plate precursor comprising:
(a) providing a printing plate precursor comprising:
(1) a substrate having a hydrophilic surface,
(2) a first layer applied to the substrate which is soluble in an aqueous alkaline solution, and
(3) a second layer applied to the first layer and including an effective amount of a quinonediazide to provide the second layer with substantial insolubility in an aqueous alkaline solution;
(b) exposing the precursor to ultraviolet light to form a white-light desensitized printing plate precursor;
(c) heating the ultraviolet light exposed precursor to form a positive-working imageable printing plate precursor;
(d) thermally imagewise exposing the heated precursor; and
(e) developing thermally imagewise exposed portions of the precursor with the aqueous alkaline solution to form a developer-resistant image.
22. The method of claim 21 wherein the aqueous alkaline solution has a pH between about 7 and 14.
23. The method of claim 21 wherein the aqueous alkaline solution has a pH of about 14.
24. The method of claim 21 wherein developing the precursor with the aqueous alkaline solution includes developing the precursor with a sodium metasilicate developer.
25. A method of forming a printing plate precursor comprising:
delivering a printing plate precursor to a customer, the precursor including:
(1) a substrate having a hydrophilic surface,
(2) a first layer applied to the substrate which is soluble in an aqueous alkaline solution, and
(3) a second layer applied to the first layer and including an effective amount of a quinonediazide to provide the second layer with substantial insolubility in an aqueous alkaline solution, wherein the precursor is exposed to ultraviolet light prior to delivery;
exposing the precursor to ultraviolet light prior to delivery to form a white light-desensitized printing plate precursor; and
heating the ultraviolet light exposed precursor prior to, during or after delivery to form a positive working printing plate precursor.
26. The method of claim 25 further comprising thermally imagewise exposing the heated precursor.
27. The method of claim 26 wherein thermally image-wise exposing the precursor consists of infrared image-wise exposing the precursor.
28. The method of claim 26 wherein thermally image-wise exposing the precursor consists of thermally image-wise exposing the precursor to radiation having a wavelength between about 800 and 1200 nm.
29. The method of claim 26 , further comprising the step of developing the thermally imagewise exposed precursor to form a printing plate.