Method of Improving Print Performance in Flexographic Printing Plates

• US 20140057207A1
• Filed: 08/27/2012
• Published: 02/27/2014
• Est. Priority Date: 08/27/2012
• Status: Active Grant

• Current Assignee: MacDermid Graphics Solutions, LLC (Element Solutions Inc)
• Original Assignee: Macdermid Printing Solutions LLC (Element Solutions Inc)
• Inventors: Baldwin, Kyle P.
• Granted Patent: US 8,790,864 B2
• Time in Patent Office: Days
• US Class Current: 430/306
• CPC Class Codes: G03F 7/201 characterised by an oblique exposure; characterised by the use of plural sources; characterised by the rotation of the optical device; characterised by a relative movement of the optical device, the light source, the sensitive system or the mask

Abstract

A method of tailoring the shape of a plurality of relief printing dots created in a photosensitive printing blank during a platemaking process is provided. The photocurable layer is exposed to actinic radiation using an array of UV LED light assemblies and the use of the array of UV LED light assemblies produces relief printing dots having at least one geometric characteristic selected from the group consisting of a desired planarity of a top surface of the relief printing dots, a desired shoulder angle of the relief printing dots and a desired edge sharpness of the relief printing dots.

Claims

1. A method of tailoring the shape of a plurality of relief printing dots created in a photosensitive printing blank during a platemaking process, said photosensitive printing blank comprising at least one photocurable layer disposed on a backing layer, the method comprising the steps of:

a) selectively exposing the at least one photocurable layer to a source of actinic radiation to selectively crosslink and cure the at least one photocurable layer; and

b) developing the exposed at least one photocurable layer of photosensitive printing blank to reveal the relief image therein, said relief image comprising the plurality of relief printing dots;

wherein the source of actinic radiation comprises an array of UV LED light assemblies, the array of UV LED light assemblies comprising rows of UV LED lights and the use of the array of UV LED light assemblies produces relief printing dots having at least one geometric characteristic selected from the group consisting of a desired planarity of a top surface of the relief printing dots, a desired shoulder angle of the relief printing dots and a desired edge sharpness of the relief printing dots, and

wherein alternate rows of UV LED lights in the array of UV LED light assemblies have different peak wavelengths.

2. The method according to claim 1, wherein the array of UV LED light assemblies comprises at least four rows.

4. The method according to claim 1, wherein the alternate rows of UV LED lights in the array of UV LED light assemblies operate at wavelengths in the range of 360 nm to 420 nm.

5. The method according to claim 1, wherein the alternate rows of UV LED lights in the array of UV LED light assemblies operate at wavelengths of 365 nm and 395 nm.

6. The method according to claim 1, wherein the at least one photocurable layer comprises a photoinitiator, wherein said photoinitiator has a UV-Vis absorption peak in the range of the operating wavelength of the UV LED light assembly.

7. The method according to claim 1, wherein alternate rows of UV LED light assemblies are arranged to have different angles of light.

8. The method according to claim 7, wherein the alternate rows of UV LED lights comprise collimated UV LED light assemblies and non-collimated UV LED light assemblies.

9. The method according to claim 1, wherein the angle of the relief printing dot shoulder is greater than about 50°

.

10. The method according to claim 1, wherein the edge sharpness of the relief printing dots, defined as the ratio of the radius of curvature r_e at the intersection of a shoulder and the top of the relief printing dot to the width of the dot'"'"'s top printing surface p is less than about 5%.

12. The method according to claim 1, wherein a bump exposure is not performed.

13. A method according to claim 1, wherein the array of UV LED light assemblies comprises at least two LED light assemblies which have peak wavelengths that are different from each other.

14. A method according to claim 1 wherein the relief printing dots comprise a planarity that is greater than a thickness of the at least one photocurable layer.

3. (canceled)

11. The method according to claim 11, wherein the ratio of r_e:

p is less than about 2%.

15. A method of tailoring the shape of a plurality of relief printing dots created in a photosensitive printing blank during a platemaking process, said photosensitive printing blank comprising at least one photocurable layer disposed on a backing layer, the method comprising the steps of:

a) selectively exposing the at least one photocurable layer to a source of actinic radiation to selectively crosslink and cure the at least one photocurable layer; and

b) developing the exposed at least one photocurable layer of photosensitive printing blank to reveal the relief image therein, said relief image comprising the plurality of relief printing dots;

wherein the source of actinic radiation comprises an array of UV LED light assemblies, the array of UV LED light assemblies comprising rows of UV LED lights, and the use of the array of UV LED light assemblies produces relief printing dots having at least one geometric characteristic selected from the group consisting of a desired planarity of a top surface of the relief printing dots, a desired shoulder angle of the relief printing dots and a desired edge sharpness of the relief printing dots, and

wherein alternate rows of UV LED lights in the array of UV LED light assemblies are arranged to have different angles of light.

16. The method according to claim 15, wherein the alternate rows of UV LED lights comprise collimated UV LED lights and non-collimated UV LED light.

17. The method according to claim 15, wherein the array of UV LED light assemblies comprises at least four rows.

18. The method according to claim 15, wherein a bump exposure is not performed.

19. The method according to claim 15, wherein the array of UV LED light assemblies comprises at least two LED light assemblies which have peak wavelengths that are different from each other.

20. (canceled)

21. (canceled)