Granted Patent B1

US 8,524,442 · App. 13/372,060 · Granted Sep 3, 2013

Abstract

Claims (48)

1. A method of exposing a photosensitive printing blank to actinic radiation in a printing plate manufacturing process, wherein the photosensitive printing blank comprises a backing layer, at least one photocurable layer disposed on the backing layer, and a laser ablatable mask layer disposed on the at least one photocurable layer, wherein the laser ablatable mask layer is laser ablated to create an in situ negative in the laser ablatable mask layer, the method comprising the steps of:

a) laminating an oxygen barrier layer to a top of the laser ablated mask layer using heat and pressure;

b) conveying the photosensitive printing blank into an exposing unit, wherein said exposing unit is capable of crosslinking and curing portions of the at least one photocurable layer not covered by the laser ablated mask layer and creating a crosslinked floor layer in the at least one photocurable layer; and

c) at least substantially simultaneously (i) exposing the at least one photocurable layer to actinic radiation from a first source of actinic radiation through the laser ablated mask layer and the oxygen barrier layer to selectively crosslink and cure portions of the at least one photocurable layer not covered by the mask layer, and (ii) exposing the at least one photocurable layer to actinic radiation from a second source of actinic radiation through the backing layer to create a crosslinked floor layer in the photocurable layer.

2. The method according to claim 1 , wherein the step of laminating the oxygen barrier layer to the top of the laser ablated mask layer comprises the steps of:

a. supplying the photosensitive printing blank to a nip formed between a heated laminating roller and a second roller;

b. supplying the oxygen barrier layer from a supply roller over an outer surface of the heated laminating roller and into the nip formed between the heated laminating roller and the second roller; wherein the oxygen barrier layer contacts a top surface of the photosensitive printing blank at a point where the photosensitive printing blank advances through the nip;

c. rotating the heated laminating roller in a first direction and the second roller in an opposite direction to advance the photosensitive printing blank with the oxygen barrier layer thereon through the nip, thereby laminating the oxygen barrier film to the top of the laser ablated mask layer.

3. The method according to claim 1 , wherein after the oxygen barrier layer is laminated to the top of the laser ablatable mask layer and the photosensitive printing blank has been exposed to actinic radiation, the method further comprises the step of removing the oxygen barrier layer.

4. The method according to claim 3 , further comprising the step of developing the imaged and exposed photosensitive printing blank to reveal a relief image therein, said relief image comprising a plurality of relief dots;

wherein the presence of the oxygen barrier layer produces printing dots having at least one geometric characteristic selected from the group consisting of planarity of a top surface of the printing dots, shoulder angle of the printing dots and edge sharpness of the printing dots, beneficially changed in relation to dots formed without the use of the oxygen barrier film.

5. The method according to claim 1 , wherein the first source of actinic radiation is selected from visible and UV sources including carbon arcs, mercury-vapor arcs, fluorescent lamps, electron flash units, electron beam units and photographic flood lamps.

6. The method according to claim 1 , wherein the first source of actinic radiation emits at a wavelength in the range of from about 250 nm to about 450 nm.

7. The method according to claim 5 , wherein the first source of actinic radiation emits at a wavelength in the range of from about 300 to about 400 nm.

8. The method according to claim 7 , wherein the first source of actinic radiation emits at a wavelength in the range of from about 320 to about 380 nm.

9. The method according to claim 1 , wherein the second source of actinic radiation is selected from visible and UV sources including carbon arcs, mercury-vapor arcs, fluorescent lamps, electron flash units, electron beam units and photographic flood lamps.

10. The method according to claim 1 , wherein the second source of actinic radiation emits at a wavelength in the range of from about 250 nm to about 450 nm.

11. The method according to claim 8 , wherein the second source of actinic radiation is attenuated, wherein the at least one photocurable layer absorbs 80% to 99% of the actinic radiation emitted by the second source of actinic radiation.

12. The method according to claim 11 , wherein the second source of actinic radiation is attenuated by a method selected from the group consisting of positioning a shutter between the second source of actinic radiation and the backing layer, by positioning a filter between the second source of actinic radiation and the backing layer, by use of a second source of actinic radiation that emits at a less efficient UV wavelength, by use of a backing layer that absorbs a portion of the actinic radiation emitted by the second source of actinic radiation and combinations of one or more of the foregoing.

13. The method according to claim 12 , wherein the second source of actinic radiation is attenuated by positioning a shutter between the second source of actinic radiation and the backing layer.

14. The method according to claim 12 , wherein the second source of actinic radiation is attenuated by positioning a filter between the second source of actinic radiation and the backing layer.

15. The method according to claim 12 , wherein the second source of actinic radiation is of a less efficient UV wavelength.

16. The method according to claim 12 , wherein the second source of actinic radiation is attenuated by using a backing layer that absorbs a portion of the actinic radiation emitted by the second source of actinic radiation.

17. The method according to claim 16 , wherein the backing layer comprises polyethylene naphthalate or doped polyethylene terephthalate.

18. The method according to claim 1 , wherein the first source of actinic radiation and the second source of actinic radiation emit at substantially the same wavelength.

19. The method according to claim 1 , wherein the first source of actinic radiation and the second source of actinic radiation emit at different wavelengths.

20. The method according to claim 2 , wherein the oxygen barrier layer comprises a material selected from the group consisting of polyamides, polyvinyl alcohol, hydroxyalkyl cellulose, copolymers of ethylene and vinyl acetate, amphoteric interpolymers, cellulose acetate butyrate, alkyl cellulose, butyral, cyclic rubbers, polypropylene, polyethylene, polyvinyl chloride, polyester and combinations of one or more of the foregoing.

21. The method according to claim 20 , where the oxygen barrier layer has an oxygen diffusion coefficient of less than 6.9×10 −9 m 2 /sec.

22. The method according to claim 20 , wherein the oxygen barrier layer has a thickness of between about 5 and about 300 microns.

23. The method according to claim 20 , wherein the oxygen barrier layer has an optical transparency of at least about 50%.

24. The method according to claim 1 , wherein the conveying speed of the photosensitive printing blank through the laminating step and the exposing unit is between about 0.5 and 5.0 feet per minute.

25. The method according to claim 1 , wherein the photosensitive printing blank is exposed to actinic radiation from the first source of actinic radiation through the in situ negative and the oxygen barrier layer for between about 1 and 20 minutes.

26. The method according to claim 1 , wherein the photosensitive printing blank is exposed to actinic radiation through the backing layer from the second source of actinic radiation for between about 1 and 5 minutes.

27. An exposing apparatus for exposing a photosensitive printing blank to actinic radiation in a printing plate manufacturing system, wherein the photosensitive printing blank comprises a backing layer, at least one photocurable layer disposed on the backing layer, and a laser ablatable mask layer disposed on the at least one photocurable layer, wherein the laser ablatable mask layer is laser ablated to create an in situ negative in the laser ablatable mask layer, the exposing apparatus comprising:

a) a laminating apparatus for laminating an oxygen barrier layer to a top of the laser ablated mask layer;

b) a conveyor for conveying the photosensitive printing blank through the exposing apparatus;

c) a first exposing device for exposing the at least one photocurable layer to actinic radiation from the first exposing device through the laser ablated mask layer and the oxygen barrier layer to selectively crosslink and cure portions of the at least one photocurable layer not covered by the mask layer, and

d) a second exposing device for exposing the at least one photocurable layer to actinic radiation from the second exposing device through the backing layer to create a crosslinked floor layer in the photocurable layer,

wherein said first exposing device and said second exposing device operate substantially simultaneously.

28. The exposing apparatus according to claim 27 , wherein the first exposing device is selected from visible and UV sources including carbon arcs, mercury-vapor arcs, fluorescent lamps, electron flash units, electron beam units and photographic flood lamps.

29. The exposing apparatus according to claim 27 , wherein the second exposing device is selected from visible and UV sources including carbon arcs, mercury-vapor arcs, fluorescent lamps, electron flash units, electron beam units and photographic flood lamps.

30. The exposing apparatus according to claim 27 , further comprising an attenuating mechanism for the second exposure device, whereby an intensity in the actinic radiation from the second exposing device is reduced.

31. The exposing apparatus according to claim 30 , wherein the attenuating mechanism comprises a shutter.

32. The exposing apparatus according to claim 30 , wherein the attenuating mechanism comprises a filter.

33. The exposing apparatus according to claim 27 , wherein the laminating apparatus comprises:

a. a heated laminating roller and a second roller, wherein said heated laminating roller and said second roller are opposably mounted and form a nip there between for receiving the photosensitive printing blank to be laminated;

b. a drive mechanism for rotating the heated laminating roller and second roller, wherein the heated laminating roller is rotated in a first direction and the second roller is rotated in an opposite direction to advance the photosensitive printing blank through the nip formed between the heated laminating roller and second roller; and

c. a supply roller adapted to support a roll of oxygen barrier layer and supply the oxygen barrier layer over an outer surface of the heated laminating roller and into the nip formed between the heated laminating roller and the second roller, wherein the oxygen barrier layer is contactable with a top surface of the photosensitive printing blank at a point where the photosensitive printing blank advances through the nip.

Assignments (11)