Flexographic Printing Plate with Improved Cure Efficiency

• US 20160131973A1
• Filed: 11/12/2014
• Published: 05/12/2016
• Est. Priority Date: 11/12/2014
• Status: Active Grant

• Current Assignee: MacDermid Graphics Solutions, LLC (Element Solutions Inc)
• Original Assignee: Macdermid Printing Solutions LLC (Element Solutions Inc)
• Inventors: Boukaftane, Chouaib
• Granted Patent: US 9,740,099 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G03F 7/029 Inorganic compounds; Onium compounds; Organic compounds having hetero atoms other than oxygen, nitrogen or sulfur
• CPC Class Codes: G03F 7/031 Organic compounds not covered by group G03F7/029
• CPC Class Codes: G03F 7/095 having more than one photosensitive layer G03F7/075 takes precedence

Abstract

A method of making a relief image printing element comprising a plurality of relief printing dots. The method includes the steps of: (a) providing at least one photocurable layer disposed on the backing layer, the at least one photocurable layer being capable of being selectively crosslinked and cured upon exposure to actinic radiation, (b) imagewise exposing the at least one photocurable layer to actinic radiation to selectively crosslink and cure portions of the at least one photocurable layer; and (c) developing the relief image printing element to separate and remove uncrosslinked and uncured portions of the at least one photocurable layer to reveal the relief image therein. The at least one photocurable layer comprises (i) an ethylenically unsaturated monomer; (ii) a binder; and (iii) a photoinitiator exhibiting a quantum yield of initiation (Qi) of more than 0.05 at a 365 nm wavelength.

Claims

1. A method of making a relief image printing element comprising a plurality of relief printing dots, the method comprising the step of:

a) providing at least one photocurable layer disposed on a backing layer, the at least one photocurable layer being capable of being selectively crosslinked and cured upon exposure to actinic radiation, the at least one photocurable layer comprising;

i) an ethylenically unsaturated monomer;

ii) a binder; and

iii) a photoinitiator, the photoinitiator exhibiting a quantum yield of initiation (Qi) of more than 0.05 at a 365 nm wavelength;

b) imagewise exposing the at least one photocurable layer to actinic radiation to selectively crosslink and cure portions of the at least one photocurable layer; and

c) developing the relief image printing element to separate and remove uncrosslinked and uncured portions of the at least one photocurable layer to reveal a relief image therein, wherein the relief image comprises the plurality of relief printing dots, and

wherein the plurality of relief printing dots exhibit an edge sharpness of the dots such that the ratio of the radius of curvature at the intersection of the shoulder and the top surface of the dot, r_e, to the width of the top of the dot, p, is less than 5%.

2. The method according to claim 1, wherein the step of imagewise exposing the at least one photocurable layer to actinic radiation is conducted in the presence of atmospheric oxygen.

3. The method according to claim 1, wherein the photoinitiator exhibits a quantum yield of initiation (Qi) greater than about 0.075 at the 365 nm wavelength.

4. The method according to claim 3, wherein the photoinitiator exhibits a quantum yield of initiation (Qi) greater than about 0.08 at the 365 nm wavelength.

5. The method according to claim 1, wherein an extinction coefficient of the photoinitiator is greater than about 300 l·

cm<sup>−

1</sup>·

mol<sup>−

1</sup> at a 365 nm wavelength.

6. The method according to claim 5, wherein the extinction coefficient of the photoinitiator is greater than about 400 l·

cm<sup>−

1</sup>·

mol<sup>−

1</sup> at the 365 nm wavelength.

7. The method according to claim 6, wherein the extinction coefficient of the photoinitiator is greater than about 500 l·

cm<sup>−

1</sup>·

mol<sup>−

1</sup> at the 365 nm wavelength.

8. The method according to claim 1, wherein the photoinitiator is selected from the group consisting of 1-butanone-2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl], 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and combinations of one or more of the foregoing.

9. The method according to claim 1, wherein the photoinitiator is present in the at least one photocurable layer at a concentration of between about 1.5 and about 5.0 percent by weight.

10. The method according to claim 9, wherein the photoinitiator is present in the at least one photocurable layer at a concentration of between about 2.0 and about 3.5 percent by weight.

11. The method according to claim 1, wherein the step of imagewise exposing the at least one photocurable layer to actinic radiation is conducted without altering of a type, power or incident angle of radiation during the exposure step.

12. A photocurable composition for producing a relief image printing element, the photocurable composition comprising:

a) an ethylenically unsaturated monomer;

b) a binder;

c) a photoinitiator, the photoinitiator exhibiting a quantum yield of initiation (Qi) of more than 0.05 at a 365 nm wavelength,

wherein the photoinitiator is selected from the group consisting of 1-butanone-2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl], 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and combinations of one or more of the foregoing.

13. The photocurable composition according to claim 12, wherein the photoinitiator exhibits a quantum yield of initiation (Qi) greater than about 0.075 at the 365 nm wavelength.

14. The photocurable composition according to claim 13, wherein the photoinitiator exhibits a quantum yield of initiation (Qi) greater than about 0.08 at the 365 nm wavelength.

15. The photocurable composition according to claim 12, wherein an extinction coefficient of the photoinitiator is greater than about 300 l·

cm<sup>−

1</sup>·

mol<sup>−

1</sup> at a 365 nm wavelength.

16. The photocurable composition according to claim 15, wherein the extinction coefficient of the photoinitiator is greater than about 400 l·

cm<sup>−

1</sup>·

mol<sup>−

1</sup> at the 365 nm wavelength.

17. The photocurable composition according to claim 16, wherein the extinction coefficient of the photoinitiator is greater than about 500 l·

cm<sup>−

1</sup>·

mol<sup>−

1</sup> at the 365 nm wavelength.

19. The photocurable composition according to claim 12, wherein the photoinitiator is present in the photocurable composition at a concentration of between about 1.5 and about 5.0 percent by weight.

20. The photocurable composition according to claim 19, wherein the photoinitiator is present in the photocurable composition at a concentration of between about 2.0 and about 3.5 percent by weight.

18. (canceled)