Method of Improving Surface Cure in Digital Flexographic Printing Plates

• US 20140057205A1
• Filed: 08/22/2012
• Published: 02/27/2014
• Est. Priority Date: 08/22/2012
• Status: Active Grant

• Current Assignee: MacDermid Graphics Solutions, LLC (Element Solutions Inc)
• Original Assignee: Macdermid Printing Solutions LLC (Element Solutions Inc)
• Inventors: Choi, Jonghan, O'Brate, Kerry
• Granted Patent: US 8,808,968 B2
• Time in Patent Office: Days
• US Class Current: 430/286.1
• CPC Class Codes: B41N 1/12 non-metallic other than stone , e.g. printing plates or foils comprising inorganic materials in an organic matrix B41N1/003, B41N1/006 take precedence
• CPC Class Codes: G03F 7/027 Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds G03F7/075 takes precedence
• CPC Class Codes: G03F 7/09 characterised by structural details, e.g. supports, auxiliary layers supports for printing plates in general B41N
• CPC Class Codes: G03F 7/20 Exposure; Apparatus therefor photographic printing apparatus for making copies G03B27/00
• CPC Class Codes: G03F 7/202 Masking pattern being obtained by thermal means, e.g. laser ablation
• CPC Class Codes: G03F 7/325 Non-aqueous compositions
• CPC Class Codes: G03F 7/36 Imagewise removal not covered by groups G03F7/30 - G03F7/34, e.g. using gas streams, using plasma

Abstract

A photocurable relief image printing element is described. The photocurable relief image printing element comprises (a) a support layer; (b) one or more photocurable layers disposed on the support layer, wherein the one or more photocurable layers comprise: (i) a binder; (ii) one or more monomers; (iii) a photoinitiator; and (iv) an additive selected from the group consisting of phosphites, phosphines, thioether amine compounds, and combinations of one or more of the foregoing; (c) a laser ablatable masking layer disposed on the one or more photocurable layers, the laser ablatable masking layer comprising a radiation opaque material; and (d) optionally, a removable coversheet. The photocurable relief image printing element provides improved surface cure in digital relief image printing elements.

Claims

1-12. -12. (canceled)

13. A method of producing a relief image printing element from a photocurable printing blank, the method comprising the steps of:

a) providing a photocurable printing blank, the photocurable printing blank comprising;

i) a backing or support layer;

ii) one or more photocurable layers disposed on the backing or support layer, wherein the one or more photocurable layers comprise;

1) a binder;

2) one or more monomers;

3) a photoinitiator; and

4) an additive selected from the group consisting of phosphites, thioether amine compounds, and combinations of one or more of the foregoing;

iii) a laser ablatable mask layer disposed on the at least one photocurable layer, the laser ablatable mask layer comprising a radiation opaque material;

b) selectively laser ablating the laser ablatable mask laser to create an in situ negative of a desired image in the laser ablatable mask layer;

c) exposing the at least one photocurable layer to actinic radiation through the in situ negative to selectively crosslink and cure portions of the at least one photocurable layer; and

d) developing the exposed at least one photocurable layer of the photocurable printing blank to reveal the relief image therein, said relief image comprising a plurality of relief printing dots.

14. The method according to claim 13, wherein the additive is a phosphite selected from the group consisting of tris(nonylphenyl)phosphite triphenyl phosphite, diphenyl phosphite, tridecyl phosphite, triisodecyl phosphite, tris(tridecyl)phosphite, trilauryl phosphite, disteraryl pentaerythriol diphosphite, diisodecyl phenyl phosphite, diphenyl isodecyl phosphite, diphenyl octyl phosphite, diphenyl isooctyl phosphite, diphenyl tri isodecyl monophenyl dipropyleneglycol diphosphite, alkyl bisphenol A phosphite, tetraphenyl dipropyleneglycol diphosphite, poly(dipropyleneglycol)phenyl phosphite, tris(dipropylene glycol)phosphite, and dioleyl hydrogen phosphite and combinations of one or more of the foregoing.

15. The method according to claim 14, wherein the additive comprises tris(nonylphenyl)phosphite.

17. The method according to claim 13, wherein the additive is a thioether amine compound selected from the group consisting of 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, 4-[[4,6-bis(nonylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(octadecylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-octylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-bis(2-methylnonan-2-yl)phenol, 4-[[4,6-bis(hexylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(heptylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl]amino]-2-tert-butyl-6-methylphenol, 4-[[4,6-bis(ethylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(2,4,4-trimethylpentan-2-ylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(2-octylsulfanylethylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-dibutylphenol, 4-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-dimethylphenol, 2,6-ditert-butyl-4-[[4-(3,5-ditert-butyl-4-hydroxyanilino)-6-octylsulfanyl-1,3,5 -triazin-2-yl]amino]phenol, 4-[[4,6-bis(pentylsulfanyl)-1,3,5-triazin-2-yl]amino-2,6-dimethylphenol, 4-[[4,6-bis(hexylsulfanyl)-1,3,5-triazin-2-yl]amino]-2-tert-butylphenol, 2,6-ditert-butyl-4-[(4-octylsulfanyl-1,3,5-triazin-2-yl)amino]phenol, 4-[[4,6-bis(ethylsulfanyl)-1,3,5-triazin-2-yl]amino]-2,6-dimethylphenol, 4-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl]-butylamino]-2,6-ditert-butylphenol, 4-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl]-cyclohexylamino]-2,6-ditert-butylphenol, 2-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl]amino]-6-tert-butylphenol, 2-tert-butyl-6-methyl-4-[[4-octylsulfanyl-6-[(2,2,6,6,-tetramethylpiperidin-4-yl)amino]-1,3,5-triazin-2-yl]amino]phenol, 4-[[4,6-bis(octylsulfanylmethyl)-1,3,5-triazin-2-yl)amino]-2,6-ditert-butylphenol, 4-[[4,6-bis(octylsulfanyl)-1,3,5-triazin-2-yl)methylamino]-2,6-ditert-butylphenol, 4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2,6-ditert-butylphenol, and 4-[(4-cyclohexyl-6-cyclohexylsulfanyl-1,3,5-triazin-2-yl)amino]-2,6-di(propan-2-yl)phenol.

18. The method according to claim 17, wherein the additive comprises 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol.

19. The method according to claim 13, wherein the at least one photocurable layer comprises an antioxidant selected from the group consisting of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, butylated hydroxytoluene, alkylated phenols, alkylated bis-phenols, polymerized trimethyldihydroquinone, dilauryl thiopropionate, and combinations of one or more of the foregoing.

20. The method according to claim 19, wherein the antioxidant comprises 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

21. The method according to claim 13, wherein the at least one photocurable layer further comprises one or more materials selected from the group consisting of plasticizers, antiozonants, fillers, reinforcing agents, thermal polymerization inhibitors, UV absorbers and combinations of one or more of the foregoing.

22. The method according to claim 21, wherein the one or more materials comprise a plasticizer.

23. The method according to claim 13, wherein the photocurable relief image printing element has a Shore A hardness of between about 45 and about 70.

24. The method according to claim 23, wherein the photocurablc relief image printing element has a Shore A hardness of between about 50 and about 65.

25. The method according to claim 13, 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%.

26. The method according to claim 25, wherein the ratio of r_e:

p is less than about 2%.

27. The method according to claim 13, wherein the planarity of the top surface of the relief printing dots, measured as the radius of curvature across the top surface of the relief printing dots and the radius of curvature across the top surface of the relief printing dots, is greater than the thickness of the at least one photocurable layer.

28. The method according to claim 13, wherein an average shoulder angle, measured as the angle between a shoulder of the dot across the width of the dot'"'"'s top or printing surface, is less than about 30°

.

29. The method according to claim 28, wherein an average shoulder angle, measured as the angle between a shoulder of the dot across the width of the dot'"'"'s top or printing surface, is less than about 20°

.

30. The method according to claim 13, wherein the exposed at least one photocurable layer is developed using solvent development.

31. The method according to claim 13, wherein the exposed at least one photocurable layer is developed using thermal development.

32. A method of producing a relief image printing element from a photocurable printing blank, the method comprising the steps of:

a) providing a photocurable printing blank, the photocurable printing blank comprising;

i) a backing or support layer;

ii) one or more photocurable layers disposed on the backing or support layer, wherein the one or more photocurable layers comprise;

1) a binder;

2) one or more monomers;

3) a photoinitiator;

4) an additive selected from the group consisting of phosphites, phosphines, thioether amine compounds, and combinations of one or more of the foregoing; and

5) an antioxidant selected from the group consisting of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, alkylated phenols, alkylated bis-phenols, polymerized trimethyldihydroquinone, dilauryl thiopropionate, and combinations of one or more of the foregoing;

iii) a laser ablatable mask layer disposed on the at least one photocurable layer, the laser ablatable mask layer comprising a radiation opaque material;

b) selectively laser ablating the laser ablatable mask laser to create an in situ negative of a desired image in the laser ablatable mask layer;

c) exposing the at least one photocurable layer to actinic radiation through the in situ negative to selectively crosslink and cure portions of the at least one photocurable layer; and

d) developing the exposed at least one photocurable layer of the photocurable printing blank to reveal the relief image therein, said relief image comprising a plurality of relief printing dots.

16. The method according to claim 32, wherein the additive is a phosphine selected from the group consisting of triphenyl phosphine, tri-p-tolylphosphine, diphenylmethylphosphine, diphenylethylphosphine, diphenylpropylphosphine, dimethylphenylphosphine, diethylphenylphosphine, dipropylphenylphosphine, divinylphenylphosphine, divinyl-p-methoxyphenylphosphine, divinyl-p-bromophenylphosphine, divinyl-p-tolylphosphine, diallylphenylphosphine, divinyl-p-bromophenylphosphine, and diallyl-p-tolylphosphine and combinations of one or more of the foregoing.